Exam 7 Draft

Created by smileykathleen 

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The centromere is a region in which
A) chromosomes are grouped during
telophase.
B) metaphase chromosomes become
aligned at the metaphase plate.
C) chromatids remain attached to one
another until anaphase.
D) new spindle microtubules form at
either end.
E) the nucleus is located prior to mitosis.

C

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
A) 16
B) 8
C) 64
D) 32
E) 4

D

If there are 20 chromatids in a cell, how many centromeres are there?
A) 40
B) 10
C) 30
D) 80
E) 20

B

For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission?
A) Cell division allows for lower rates of error per chromosome replication.
B) Cell division would be faster than
binary fission.
C) Cell division would allow for the
orderly and efficient segregation of
multiple linear chromosomes.
D) Binary fission would not allow for the formation of new organisms.
E) Binary fission would not allow the
organism to have complex cells.

C

Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal) nucleus. It might consist of which of the following?
A) two chromosomes, each with six
chromatids
B) two chromatids attached together at a
centromere
C) two long strands of DNA plus proteins
D) one-twelfth of the genes of the
organism
E) a single circular piece of DNA

C

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
A) centrosome
B) centriole
C) centromere
D) kinetochore
E) chromatid

A

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per
nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?
A) G 1
B) G 0
C) S
D) M
E) G 2

E

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2?
A) 8; 16
B) 8; 8
C) 16; 8
D) 12; 16
E) 16; 16

E

Why do chromosomes coil during mitosis?
A) to allow the chromosomes to move
without becoming entangled and
breaking
B) to allow the chromosomes to fit within
the nuclear envelope
C) to provide for the structure of the
centromere
D) to increase their potential energy
E) to allow the sister chromatids to
remain attached

B

Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?
A) Motor proteins of the kinetochores
move the chromosomes along the
spindle microtubules.
B) Nonkinetochore spindle fibers serve to
push chromosomes in the direction of
the poles.
C) The chromosomes are "reeled in" by the
contraction of spindle microtubules,
and motor proteins of the kinetochores
move the chromosomes along the
spindle microtubules.
D) The chromosomes are "reeled in" by the
contraction of spindle microtubules.
E) The chromosomes are "reeled in" by the
contraction of spindle microtubules,
motor proteins of the kinetochores
move the chromosomes along the
spindle microtubules, and
nonkinetochore spindle fibers serve to
push chromosomes in the direction of
the poles.

A

What causes the decrease in the amount of cyclin at a specific point in the cell cycle?
A) the cascade of increased production
once its protein is phosphorylated by
Cdk
B) the changing ratio of cytoplasm to
genome
C) its destruction by a process initiated by
the activity of its complex with a cyclin
D) an increase in production once the
restriction point is passed
E) the binding of PDGF to receptors on
the cell surface

C

Which of the following is a protein
maintained at constant levels throughout the cell cycle that requires cyclin to become
catalytically active?
A) PDGF
B) MPF
C) protein kinase
D) Cdk
E) cyclin

D

Which of the following is true concerning cancer cells?
A) When they stop dividing, they do so at
random points in the cell cycle, and
they are not subject to cell cycle
controls.
B) They do not exhibit density-dependent
inhibition when growing in culture.
C) When they stop dividing, they do so at
random points in the cell cycle; they
are not subject to cell cycle controls;
and they do not exhibit
density-dependent inhibition when
growing in culture.
D) When they stop dividing, they do so at
random points in the cell cycle.
E) They are not subject to cell cycle
controls.

C

Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
A) inability to form spindles
B) changes in the order of cell cycle stages
C) metastasis
D) lack of appropriate cell death
E) inability of chromosomes to meet at the
metaphase plate

D

After which checkpoint is the cell first
committed to continue the cell cycle through M?
A) S
B) G 1
C) G 0
D) previous M
E) G 2

B

All cell cycle checkpoints are similar in which way?
A) They each have only one cyclin/Cdk
complex.
B) They utilize the same Cdks.
C) They respond to the same cyclins.
D) They give the go-ahead signal to
progress to the next checkpoint.
E) They activate or inactivate other
proteins.

D

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
A) It is safe enough to limit all apoptosis.
B) It only attacks cells that are density
dependent.
C) It interferes with rapidly dividing cells.
D) It interferes with cells entering G0.
E) It does not alter metabolically active
cells.

C

In the figure above, mitosis is represented by which numbered part(s) of the cycle?
A) I
B) II
C) III
D) IV
E) V

D

G 1 is represented by which numbered part(s) of the cycle?
A) I or V
B) II or IV
C) III only
D) IV only
E) V only

A

Which number represents DNA synthesis?
A) I
B) II
C) III
D) IV
E) V

B

Which number represents the point in the cell cycle during which the chromosomes are replicated?
A) I
B) II
C) III
D) IV
E) V

B

Of the following, the best conclusion
concerning the difference between the S phases for beta and gamma is that
A) gamma contains more DNA than beta.
B) beta and gamma contain the same
amount of DNA.
C) beta cells reproduce asexually.
D) beta is a plant cell and gamma is an
animal cell.
E) gamma contains 48 times more DNA
and RNA than beta.

A

The best conclusion concerning delta is that the cells
A) contain only one chromosome that is
very short.
B) divide in the G 1 phase.
C) contain no RNA.
D) contain no DNA.
E) are actually in the G0 phase.

E

One difference between cancer cells and normal cells is that cancer cells
A) are always in the M phase of the cell
cycle.
B) are unable to synthesize DNA.
C) are arrested at the S phase of the cell
cycle.
D) cannot function properly because they
are affected by density-dependent
inhibition.
E) continue to divide even when they are
tightly packed together.

E

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
A) cells lacking nuclei.
B) cells with more than one nucleus.
C) cell cycles lacking an S phase.
D) destruction of chromosomes.
E) cells that are unusually small.

B

Which of the following does not occur during mitosis?
A) condensation of the chromosomes
B) separation of sister chromatids
C) spindle formation
D) replication of the DNA
E) separation of the spindle poles

D

The human genome is minimally contained
in which of the following?
A) the entire DNA of a single human
B) the entire human population
C) each human gene
D) each human chromosome
E) every human cell

E

In the human species, all somatic cells have 46 chromosomes. Which of the following can also be true?
A) A certain fungal species has only one
chromosome per cell.
B) Some adult humans have 23
chromosomes per cell.
C) A certain bacterial species has 23
chromosomes.
D) Some adult humans have 69
chromosomes per cell.
E) A plant species (privet shrubs) has 46
chromosomes per cell.

B

Which of the following is a true statement
about sexual vs. asexual reproduction?
A) In asexual reproduction, offspring are
produced by fertilization without
meiosis.
B) Asexual reproduction produces only
haploid offspring.
C) Asexual reproduction, but not sexual
reproduction, is characteristic of plants
and fungi.
D) In sexual reproduction, individuals
transmit 50% of their genes to each of
their offspring.
E) Sexual reproduction requires that
parents be diploid.

D

Which of the following defines a genome?
A) representation of a complete set of a
cell's polypeptides
B) the complete set of an organism's genes
C) a karyotype
D) the complete set of a species'
polypeptides
E) the complete set of an organism's
polypeptides

B

The human X and Y chromosomes
A) include genes that determine an
individual's sex.
B) are almost entirely homologous,
despite their different names.
C) are both present in every somatic cell of
males and females alike.
D) are of approximately equal size and
number of genes.
E) include only genes that govern sex
determination.

A

Which of the following is true of a species that has a chromosome number of 2n = 16?
A) During the S phase of the cell cycle
there will be 32 separate chromosomes.
B) The species has 16 sets of chromosomes
per cell.
C) A gamete from this species has four
chromosomes.
D) The species is diploid with 32
chromosomes per cell.
E) Each cell has eight homologous pairs.

E

Eukaryotic sexual life cycles show
tremendous variation. Of the following
elements, which do all sexual life cycles have in common?
I. Alternation of generations
II. Meiosis
III. Fertilization
IV. Gametes
V. Spores
A) II, IV, and V
B) I, II, III, IV, and V
C) I, II, and IV
D) II, III, and IV
E) I, IV, and V

D

Referring to a plant's sexual life cycle, which of the following terms describes the process that leads directly to the formation of gametes?
A) gametophyte mitosis
B) gametophyte meiosis
C) sporophyte mitosis
D) alternation of generations
E) sporophyte meiosis

A

Which of the following is an example of
alternation of generations?
A) A diploid animal produces gametes by
meiosis, and the gametes undergo
fertilization to produce a diploid
zygote.
B) A grandparent and grandchild each
have dark hair, but the parent has
blond hair.
C) A diploid plant (sporophyte) produces,
by meiosis, a spore that gives rise to a multicellular, haploid pollen grain
(gametophyte).
D) A haploid mushroom produces
gametes by mitosis, and the gametes
undergo fertilization, which is
immediately followed by meiosis.
E) A diploid cell divides by mitosis to
produce two diploid daughter cells,
which then fuse to produce a tetraploid
cell.

C

A given organism has 46 chromosomes in its
karyotype. We can therefore conclude which
of the following?
A) It must be sexually reproducing.
B) It must be a primate.
C) It must be an animal.
D) It must be human.
E) Its gametes must have 23
chromosomes.

E

A triploid cell contains three sets of
chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following?
A) 63 chromosomes in 31 1/2 pairs
B) 63 chromosomes, each with three
chromatids
C) 21 chromosome pairs and 21 unique
chromosomes
D) 63 chromosomes in 21 sets of 3

D

A karyotype results from which of the
following?
A) the ordering of human chromosome images
B) the separation of homologous
chromosomes at metaphase I of
meiosis
C) the cutting and pasting of parts of
chromosomes to form the standard
array
D) an inherited ability of chromosomes to arrange themselves
E) a natural cellular arrangement of
chromosomes in the nucleus

A

Which of the following best describes a karyotype?
A) the collection of all the chromosomes in an individual organism
B) a photograph of all the cells with
missing or extra chromosomes
C) a display of each of the chromosomes of a single cell
D) a pictorial representation of all the
genes for a species
E) the combination of all the maternal and paternal chromosomes of a species

C

If a cell has completed the first meiotic
division and is just beginning meiosis II, which of the following is an appropriate description of its contents?
A) It has half the amount of DNA as the
cell that began meiosis.
B) It has one-fourth the DNA and
one-half the chromosomes as the
originating cell.
C) It has the same number of
chromosomes but each of them has
different alleles than another cell from
the same meiosis.
D) It has half the chromosomes but twice
the DNA of the originating cell.
E) It is identical in content to another cell
from the same meiosis.

A

Which of the following might result in a human zygote with 45 chromosomes?
A) failure of the egg nucleus to be
fertilized by the sperm
B) an error in either egg or sperm meiotic anaphase
C) lack of chiasmata in prophase I
D) an error in the alignment of
chromosomes on the metaphase plate
E) fertilization of a 23 chromosome
human egg by a 22 chromosome sperm
of a closely related species

B

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?
A) Length, centromere position, and
staining pattern only.
B) Length and position of the centromere only.
C) They have nothing in common except they are X-shaped.
D) Length, centromere position, staining pattern, and traits coded for by their genes.
E) Length, centromere position, staining pattern, and DNA sequences.

A

compare with cells that have replicated their DNA and are just about to begin meiosis?
A) They have half the number of
chromosomes and one-fourth the
amount of DNA.
B) They have half the amount of
cytoplasm and twice the amount of DNA.
C) They have half the number of
chromosomes and half the amount of
DNA.
D) They have the same number of
chromosomes and half the amount of
DNA.
E) They have twice the amount of
cytoplasm and half the amount of
DNA.

A

Which of the following happens at the
conclusion of meiosis I?
A) Homologous chromosomes are
separated.
B) Four daughter cells are formed.
C) The chromosome number per cell is conserved.
D) Sister chromatids are separated.
E) The sperm cells elongate to form a
head and a tail end.

A

A cell divides to produce two daughter cells that are genetically different.
A) The statement is true for meiosis I only.
B) The statement is true for mitosis and meiosis I.
C) The statement is true for meiosis II
only.
D) The statement is true for mitosis only.
E) The statement is true for mitosis and meiosis II.

A

Chromatids are separated from each other.
A) The statement is true for mitosis only.
B) The statement is true for mitosis and meiosis II.
C) The statement is true for meiosis II
only.
D) The statement is true for mitosis and meiosis I.
E) The statement is true for meiosis I only.

C

Independent assortment of chromosomes occurs.
A) The statement is true for mitosis only.
B) The statement is true for mitosis and meiosis I.
C) The statement is true for meiosis II
only.
D) The statement is true for mitosis and meiosis II.
E) The statement is true for meiosis I only.

E

If an organism is diploid and a certain gene found in the organism has 18 known alleles (variants), then any given organism of that species can/must have which of the following?
A) up to 18 chromosomes with that gene
B) a haploid number of 9 chromosomes
C) up to 18 genes for that trait
D) at most, 2 alleles for that gene
E) up to, but not more than, 18 different traits

D

1. Formation of four new nuclei, each with half the chromosomes present in the parental nucleus
2. Alignment of tetrads at the metaphase plate
3. Separation of sister chromatids
4. Separation of the homologs; no uncoupling of the centromere
5. Synapsis; chromosomes moving to the middle of the cell in pairs
Which of the steps takes place in both mitosis and meiosis?
A) 2
B) 3
C) 5
D) 2 and 3 only
E) 2, 3, and 5

C

How does the sexual life cycle increase the genetic variation in a species?
A) by decreasing mutation frequency
B) by allowing fertilization
C) by allowing crossing over
D) by increasing gene stability
E) by conserving chromosomal gene order

C

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?
A) 23
B) 460
C) 920
D) about 8 million
E) 46

E

Independent assortment of chromosomes is a result of
A) the random distribution of the sister chromatids to the two daughter cells during anaphase II.
B) the random and independent way in which each pair of homologous
chromosomes lines up at the
metaphase plate during meiosis I.
C) the relatively small degree of
homology shared by the X and Y
chromosomes.
D) the random nature of the fertilization of ova by sperm.
E) the random and independent way in which each pair of homologous
chromosomes lines up at the metaphase plate during meiosis I, the
random nature of the fertilization of
ova by sperm, the random distribution
of the sister chromatids to the two
daughter cells during anaphase II, and the relatively small degree of
homology shared by the X and Y
chromosomes.

B

Which of the following best describes the frequency of crossing over in mammals?
A) ~50 per chromosome pair
B) ~1 per pair of sister chromatids
C) at least 1-2 per chromosome pair
D) ~2 per meiotic cell
E) a very rare event among hundreds of
cells

C

When homologous chromosomes crossover, what occurs?
A) Two chromatids get tangled, resulting in one re-sequencing its DNA.
B) Maternal alleles are "corrected" to be like paternal alleles and vice versa.
C) Each of the four DNA strands of a
tetrad is broken and the pieces are
mixed.
D) Two sister chromatids exchange
identical pieces of DNA.
E) Specific proteins break the two strands
and re-join them with their homologs.

C

Which of the life cycles is typical for animals?
A) I only
B) II only
C) III only
D) I and II
E) I and III

A

Which of the life cycles is typical for plants and some algae?
A) I only
B) II only
C) III only
D) I and II
E) I and III

C

Which of the life cycles is typical for most fungi and some protists?
A) I only
B) II only
C) III only
D) I and II
E) I and III

B

There is a group of invertebrate animals called rotifers, among which a particular group of species reproduces, as far as is known, only asexually. These rotifers, however, have survived a long evolutionary history without evidence of having been overcome by excessive mutations.
Since the rotifers develop from eggs, but asexually, what can you predict?
A) The eggs and the zygotes are all
haploid.
B) All males can produce eggs.
C) The animals are all hermaphrodites.
D) While asexual, both males and females are found in nature.
E) No males can be found.

C

There is a group of invertebrate animals called rotifers, among which a particular group of species reproduces, as far as is known, only asexually. These rotifers, however, have survived a long evolutionary history without evidence of having been overcome by excessive mutations.
Assuming that the eggs are diploid,
tetraploid, or partially tetraploid, what
mechanism may still occur without
fertilization?
A) meiosis in every second generation
B) meiosis in times of adverse
environmental conditions
C) independent assortment of maternal and paternal chromosomes
D) crossing over of homologs
E) meiosis in each generation

D

There is a group of invertebrate animals called rotifers, among which a particular group of species reproduces, as far as is known, only asexually. These rotifers, however, have survived a long evolutionary history without evidence of having been overcome by excessive mutations.
In these asexual rotifers, how does variation occur without meiosis and fertilization?
A) Some rotifers must selectively lose
chromosomes.
B) Variation is caused by mutation and maintained by selection.
C) Rotifers must live only in specialized environments.
D) Rotifers must produce haploid spores.
E) The rotifers have evolved a different
mechanism to exchange DNA.

B

How is natural selection related to sexual reproduction as opposed to asexual reproduction?
A) Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction.
B) Sexual reproduction results in the
greatest number of new mutations.
C) Sexual reproduction utilizes far less energy than asexual reproduction.
D) Sexual reproduction results in the most appropriate and healthiest balance of two sexes in the population.
E) Sexual reproduction allows the greatest number of offspring to be produced.

A

A human cell containing 22 autosomes and a Y chromosome is
A) a somatic cell of a female.
B) an egg.
C) a zygote.
D) a somatic cell of a male.
E) a sperm.

E

Homologous chromosomes move toward opposite poles of a dividing cell during
A) fertilization.
B) meiosis II.
C) binary fission.
D) meiosis I.
E) mitosis.

D

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of a single cell at metaphase of meiosis II would be
A) x.
B) 2x.
C) 4x.
D) 0.25x.
E) 0.5x.

B

What do we mean when we use the terms monohybrid cross and dihybrid cross?
A) A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid cross involves only one.
B) A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny.
C) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations.
D) A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio.
E) A monohybrid cross involves a single parent, whereas a dihybrid cross
involves two parents.

A

How many unique gametes could be
produced through independent assortment by an individual with the genotype AaBbCCDdEE?
A) 4
B) 32
C) 64
D) 8
E) 16

D

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?
A) crossing over during prophase I
B) the tendency for dominant alleles to segregate together
C) different possible alignments of
chromosomes
D) recurrent mutations forming new
alleles
E) segregation of maternal and paternal alleles

C

Which of the following differentiates
between independent assortment and
segregation?
A) The law of segregation requires having two or more generations to describe.
B) The law of independent assortment
requires describing two or more genes relative to one another.
C) The law of independent assortment is accounted for by observations of prophase I.
D) The law of segregation requires
describing two or more genes relative
to one another.
E) The law of segregation is accounted for by anaphase of mitosis.

B

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?
A) that the trait shows incomplete
dominance
B) that the parents were both
heterozygous for a single trait
C) that a blending of traits has occurred
D) that each offspring has the same alleles for each of two traits
E) that the parents were true-breeding for contrasting traits

B

A sexually reproducing animal has two
unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt.
Which of the following genotypes is possible in a gamete from this organism?
A) tt
B) HhTt
C) T
D) HT
E) Hh

D

When crossing an organism that is
homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
A) 100%
B) 50%
C) 25%
D) 0%
E) 75%

B

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
A) The formation of gametes in plants
occurs by mitosis only.
B) None of the traits obeyed the law of segregation.
C) All of the genes controlling the traits were located on the same chromosome.
D) The diploid number of chromosomes in the pea plants was 7.
E) All of the genes controlling the traits behaved as if they were on different chromosomes.

E

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have
black fur and long tails?
A) 9/16
B) 3/16
C) 3/8
D) 1/16
E) 1/2

E

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
A) 1/4
B) 1/6
C) 1
D) 1/2
E) 0

E

In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
A) 1/4
B) 1/32
C) 1/16
D) 1/8
E) 1/64

E

Given the parents AABBCc × AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?
A) 3/8
B) 3/4
C) 1/8
D) 1/4
E) 1

B

Which of the following is the best statement of the use of the addition rule of probability?
A) the likelihood that a trait is due to two or more meiotic events
B) the probability of producing two or
more heterozygous offspring
C) the probability that two or more
independent events will both occur
D) the probability that two or more
independent events will both occur in
the offspring of one set of parents
E) the probability that either one of two
independent events will occur

E

Which of the following calculations require that you utilize the addition rule?
A) Calculate the probability of black
offspring from the cross AaBb × AaBb, when B is the symbol for black.
B) Calculate the probability of each of
four children having cystic fibrosis if
the parents are both heterozygous.
C) Calculate the probability of children with both cystic fibrosis and
polydactyly when parents are each
heterozygous for both genes.
D) Calculate the probability of a child
having either sickle-cell anemia or
cystic fibrosis if parents are each
heterozygous for both.
E) Calculate the probability of purple
flower color in a plot of 50 plants
seeded from a self-fertilizing
heterozygous parent plant.

D

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses
would produce offspring in the ratio of 1 red:2 roan:1 white?
A) white × roan
B) red × roan
C) roan × roan
D) red × white
E) The answer cannot be determined from
the information provided.

C

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections.
Which of the following terms best describes this?
A) codominance
B) epistasis
C) pleiotropy
D) incomplete dominance
E) multiple alleles

C

Which of the following is an example of polygenic inheritance?
A) pink flowers in snapdragons
B) white and purple flower color in peas
C) the ABO blood group in humans
D) Huntington's disease in humans
E) skin pigmentation in humans

E

Which of the following provides an example of epistasis?
A) Recessive genotypes for each of two genes (aabb) results in an albino corn snake.
B) In rabbits and many other mammals, one genotype (cc) prevents any fur color from developing.
C) The allele b17 produces a dominant phenotype, although b1 through b16 do not.
D) In cacti, there are several genes for the type of spines.
E) In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes.

B

Most genes have many more than two alleles. However, which of the following is also true?
A) There may still be only two phenotypes for the trait.
B) More than two alleles in a genotype is considered lethal.
C) Most of the alleles will never be found in a live-born organism.
D) At least one allele for a gene always produces a dominant phenotype.
E) All of the alleles but one will produce harmful effects if homozygous.

A

How could you best predict the maximum number of alleles for a single gene whose polypeptide product is known?
A) Measure the rate of new mutations in the species and estimate the number since it first evolved.
B) Count the number of DNA nucleotides that are in the code for the polypeptides.
C) Count the number of amino acids in the polypeptide.
D) Search the population for all
phenotypic variants of this polypeptide.
E) Mate all known genotypes and collect all possible offspring different from the parents.

B

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F 1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.
Which of the boxes marked 1-4 correspond to plants with dark leaves?
A) 1, 2, and 3
B) 1 only
C) 2 and 3
D) 1 and 2
E) 4 only

A

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F 1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.
Which of the boxes correspond to plants with a heterozygous genotype?
A) 1, 2, and 3
B) 1
C) 2, 3, and 4
D) 2 and 3
E) 1 and 2

D

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F 1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.
Which of the plants will be true-breeding?
A) 1, 2, 3, and 4
B) 1 and 2 only
C) 2 and 3 only
D) 1 only
E) 1 and 4 only

E

What is the genotype of individual II-5?
A) ww or Ww
B) WW
C) ww
D) Ww
E) WW or ww

C

What is the likelihood that the progeny of IV-3 and IV-4 will have the trait?
A) 100%
B) 0%
C) 75%
D) 50%
E) 25%

D

What is the probability that individual III-1 is Ww?
A) 3/4
B) 2/4
C) 1
D) 1/4
E) 2/3

C

What is the genotype of the deceased
individual in generation II?
A) homozygous for a gene for colon
cancer
B) heterozygous for a gene for colon
cancer
C) homozygous for both cancer alleles from his mother
D) affected by the same colon cancer
environmental factor as his mother
E) carrier of all of the several known
genes for colon cancer

A

From this pedigree, how does this trait seem to be inherited?
A) as an incomplete dominant
B) from mothers
C) as an autosomal dominant
D) as a result of epistasis
E) as an autosomal recessive

E

The affected woman in generation IV is thinking about her future and asks her oncologist (cancer specialist) whether she can know whether any or all of her children will have a high risk of the same cancer. The doctor would be expected to advise which of
the following?
I. genetic counseling
II. prenatal diagnosis when/if she becomes pregnant
III. testing to see whether she has the allele
IV. testing to see whether her future spouse or partner has the allele
A) I, II, and III only
B) I and II only
C) I only
D) II only
E) III and IV only

B

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers.The genes for flower color and location assort independently.
If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?
A) 190
B) 750
C) 65
D) 565
E) 250

A

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers.The genes for flower color and location assort independently.
Among the F2 offspring, what is the
probability of plants with white axial
flowers?
A) 3/16
B) 1/16
C) 1/8
D) 9/16
E) 1/4

A

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be expected to be which of the following?
A) red and oval
B) purple and oval
C) purple and long
D) white and long
E) red and long

C

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant characteristic.
The flower color trait in radishes is an
example of which of the following?
A) codominance
B) incomplete dominance
C) epistasis
D) a multiple allelic system
E) sex linkage

B

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color.
A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F 1 individuals?
A) TtRr—tall and red
B) TTRR—tall and red
C) TtRr—tall and pink
D) ttRr—dwarf and pink
E) ttrr—dwarf and white

C

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color.
If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio?
A) 9:3:3:1
B) 27:9:9:9:3:3:3:1
C) 9:4:3
D) 6:3:3:2:1:1
E) 1:2:1

A

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull
spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
The relationship between genes S and N is an example of
A) incomplete dominance.
B) pleiotropy.
C) complete dominance.
D) epistasis.
E) codominance.

D

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull
spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
A cross between a true-breeding
sharp-spined cactus and a spineless cactus would produce
A) all sharp-spined progeny.
B) 50% sharp-spined, 50% dull-spined progeny.
C) all spineless progeny.
D) 25% sharp-spined, 50% dull-spined, 25% spineless progeny.
E) It is impossible to determine the
phenotypes of the progeny.

A

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull
spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would
segregate in which of the following ratios?
A) 1 sharp-spined:1 dull-spined
B) 1 sharp-spined:1 dull-spined:1
spineless
C) 1 sharp-spined:2 dull-spined:1
spineless
D) 9 sharp-spined:3 dull-spined:4
spineless
E) 3 sharp-spined:1 spineless

D

Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white.
A blue budgie is crossed with a white
budgie. Which of the following results is not possible?
A) a 9:3:3:1 ratio
B) green offspring only
C) blue offspring only
D) yellow offspring only
E) green and yellow offspring

E

Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white.
Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?
A) yyBB and yybb
B) yyBb and yyBb
C) yyBB and yyBB
D) yyBB and yyBb
E) yyBb and yybb

B

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible partial genotype for the son?
A) IAIA
B) IBIB
C) IBIA
D) ii
E) IBi

E

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible genotypefor the mother?
A) IAIA
B) IAi
C) IBIB
D) IAIB
E) ii

B

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible
phenotype for the father?
A) O negative
B) AB negative
C) A negative
D) B positive
E) impossible to determine

D

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
If both children are of blood type M, which of the following is possible?
A) Each parent must be type M.
B) Each parent is either M or MN.
C) The MN blood group is recessive to the ABO blood group.
D) Both children are heterozygous for this gene.
E) Neither parent can have the N allele.

B

The role of a metabolite that controls a repressible operon is to
A) bind to the repressor protein and
activate it.
B) bind to the promoter region and
decrease the affinity of RNA polymerase for the promoter.
C) increase the production of inactive
repressor proteins.
D) bind to the repressor protein and
inactivate it.
E) bind to the operator region and block the attachment of RNA polymerase to
the promoter.

E

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in
A) continuous translation of the mRNA
because of alteration of its structure.
B) inactivation of RNA polymerase by
alteration of its active site.
C) continuous transcription of the
structural gene controlled by that
regulator.
D) irreversible binding of the repressor to the operator.
E) complete inhibition of transcription of the structural gene controlled by that regulator.

C

Transcription of the structural genes in an inducible operon
A) occurs continuously in the cell.
B) does not result in the production of
enzymes.
C) starts when the pathway's substrate is present.
D) starts when the pathway's product is present.
E) stops when the pathway's product is present.

C

For a repressible operon to be transcribed, which of the following must occur?
A) A corepressor must be present.
B) RNA polymerase cannot be present, and the repressor must be inactive.
C) RNA polymerase and the active
repressor must be present.
D) RNA polymerase must not occupy the promoter, and the repressor must be inactive.
E) RNA polymerase must bind to the
promoter, and the repressor must be
inactive.

E

Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways?
A) allowing young organisms to respond differently from more mature
organisms
B) organizing gene expression so that
genes are expressed in a given order
C) allowing each gene to be expressed an equal number of times
D) allowing the organism to adjust to
changes in environmental conditions
E) allowing environmental changes to
alter the prokaryote's genome

D

If you were to observe the activity of
methylated DNA, you would expect it to
A) be very actively transcribed and
translated.
B) be unwinding in preparation for
protein synthesis.
C) induce protein synthesis by not
allowing repressors to bind to it.
D) have turned off or slowed down the
process of transcription.
E) be replicating nearly continuously.

D

When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene
expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?
A) DNA supercoiling at or around H1
B) hydrolysis of DNA molecules where
they are wrapped around the
nucleosome core
C) accessibility of heterochromatin to
phosphorylating enzymes
D) methylation and phosphorylation of
histone tails
E) nucleotide excision and reconstruction

D

In eukaryotes, general transcription factors
A) usually lead to a high level of
transcription even without additional
specific transcription factors.
B) are required for the expression of
specific protein-encoding genes.
C) inhibit RNA polymerase binding to the promoter and begin transcribing.
D) bind to other proteins or to a sequence element within the promoter called the TATA box.
E) bind to sequences just after the start site of transcription.

D

Steroid hormones produce their effects in cells by
A) binding to intracellular receptors and promoting transcription of specific
genes.
B) activating translation of certain mRNAs.
C) activating key enzymes in metabolic pathways.
D) promoting the formation of looped
domains in certain regions of DNA.
E) promoting the degradation of specific mRNAs.

A

Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following?
A) Eukaryotic mRNAs get 5' caps and 3' tails.
B) Eukaryotic coded polypeptides often require cleaving of signal sequences before localization.
C) Eukaryotic exons may be spliced in
alternative patterns.
D) Prokaryotes use ribosomes of different structure and size.
E) Prokaryotic genes are expressed as mRNA, which is more stable in the cell.

C

The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced
double-stranded RNA is called
A) RNA targeting.
B) RNA obstruction.
C) RNA blocking.
D) RNA interference.
E) RNA disposal.

D

Which of the following best describes
siRNA?
A) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
B) a molecule, known as Dicer, that can degrade other mRNA sequences
C) a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
D) a portion of rRNA that allows it to bind to several ribosomal proteins in
forming large or small subunits
E) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns

C

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to
gain most from RNAs?
A) creating knock-out organisms that can be useful for pharmaceutical drug
design
B) exploring a way to turn on the
expression of pseudogenes
C) targeting siRNAs to disable the
expression of an allele associated with autosomal recessive disease
D) looking for a way to prevent viral DNA from causing infection in humans
E) targeting siRNAs to disable the
expression of an allele associated with autosomal dominant disease

E

Muscle cells differ from nerve cells mainly because they
A) have different chromosomes.
B) contain different genes.
C) express different genes.
D) have unique ribosomes.
E) use different genetic codes.

C

The functioning of enhancers is an example of
A) a post-transcriptional mechanism to regulate mRNA.
B) a eukaryotic equivalent of prokaryotic promoter functioning.
C) the stimulation of translation by
initiation factors.
D) transcriptional control of gene expression.
E) post-translational control that activates certain proteins.

D

Which of the following is an example of post-transcriptional control of gene
expression?
A) the removal of introns and alternative splicing of exons
B) the binding of transcription factors to a promoter
C) the addition of methyl groups to
cytosine bases of DNA
D) gene amplification contributing to
cancer
E) the folding of DNA to form
heterochromatin

A

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?
A) Cells produce proto-oncogenes as they age.
B) Proto-oncogenes normally help
regulate cell division.
C) Proto-oncogenes are mutant versions of normal genes.
D) Proto-oncogenes first arose from viral infections.
E) Proto-oncogenes are genetic "junk."

B

Which of the following is the correct
sequence during the alternation of
generations life cycle in a flowering plant?
A) haploid gametophyte → gametes →meiosis → fertilization → diploid
sporophyte
B) sporophyte → mitosis → gametophyte→ meiosis → sporophyte
C) sporophyte → meiosis → gametophyte→ gametes→fertilization → diploid zygote
D) haploid sporophyte → spores →
fertilization → diploid gametophyte
E) sporophyte → spores → meiosis →gametophyte → gametes

C

Which of the following are true of mostangiosperms?
A) They have a triploid endosperm within the seed, an ovary that becomes a fruit, and a small (reduced) sporophyte.
B) They have an ovary that becomes a fruit.
C) They have a small (reduced)
sporophyte.
D) They have a triploid endosperm within the seed and an ovary that becomes a fruit.
E) They have a triploid endosperm within the seed.

D

All of the following floral parts are involved in pollination or fertilization except the
A) petals.
B) sepals.
C) carpel.
D) stamen.
E) receptacle.

B

The ovary is most often located on/in the
A) receptacle.
B) petals.
C) sepals.
D) carpel.
E) stamen.

D

Microsporangia in flowering plants are
located in the
A) receptacle.
B) petals.
C) stamen.
D) carpel.
E) sepals.

C

Which of the following is the correct order of floral organs from the outside to the inside of a complete flower?
A) sepals → petals → stamens → carpels
B) spores → gametes → zygote → embryo
C) petals → sepals → stamens → carpels
D) male gametophyte → female
gametophyte → sepals → petals
E) sepals → stamens → petals → carpels

A

Which of the following statements regarding flowering plants is false?
A) Female gametophytes develop from megaspores within the anthers.
B) The sporophyte is the dominant
generation.
C) Pollination is the placing of pollen on the stigma of a carpel.
D) Flowers produce fruits within the
ovules.
E) The food-storing endosperm is derived from the cell that contains two polar nuclei and one sperm nucleus.

A

In flowering plants, pollen is released from the
A) stigma.
B) filament.
C) anther.
D) pollen tube.
E) carpel.

C

Which of the following is a correct sequence of processes that takes place when a flowering plant reproduces?
A) meiosis → pollination → nuclear
fusion → formation of embryo and
endosperm
B) meiosis → fertilization → ovulation → germination
C) meiosis → mitosis → nuclear fusion → pollen
D) fertilization → meiosis → nuclear
fusion → formation of embryo and
endosperm
E) growth of pollen tube → pollination → germination → fertilization

A

Which of the following is incorrectly paired with its life-cycle generation?
A) embryosporophyte
B) stamensporophyte
C) pollengametophyte
D) embryo sacgametophyte
E) anthergametophyte

E

Which of the following is the correct
sequence of events in a pollen sac?
A) two haploid cells → meiosis →
generative cell → tube cell-fertilization
→ pollen grain
B) sporangia → meiosis → two haploid cells → meiosis → two pollen grains per cell
C) microsporocyte → meiosis →
microspores → mitosis → two haploid
cells per pollen grain
D) pollen grain → mitosis → microspores → meiosis → generative cell plus tube cell
E) pollen grain → meiosis → two
generative cells → two tube cells per
pollen grain

C

Where and by which process are sperm cells formed in plants?
A) mitosis in the micropyle
B) meiosis in anthers
C) mitosis in male gametophyte pollen
tube
D) meiosis in pollen grains
E) mitosis in the embryo sac

C

In flowering plants, a mature male
gametophyte contains
A) two haploid gametes and a diploid
pollen grain.
B) a generative cell and a tube cell.
C) two sperm nuclei and one tube cell
nucleus.
D) a haploid nucleus and a diploid pollen wall.
E) two haploid microspores.

C

What is the difference between pollination and fertilization in flowering plants?
A) If fertilization occurs, pollination is
unnecessary.
B) Pollination is the transfer of pollen
from an anther to a stigma.
Fertilization is the fusion of haploid
nuclei.
C) Fertilization precedes pollination.
D) Pollen is formed within megasporangia so that male and female gametes are near each other.
E) Pollination easily occurs between
plants of different species, whereas
fertilization is within a species.

B

Recent research has shown that pollination requires that carpels recognize pollen grains as "self or nonself." For self-incompatibility, the system requires
A) carpel incompatibility with the egg
cells.
B) the union of genetically identical sperm and egg cells.
C) that the flowers be incomplete.
D) the rejection of nonself cells.
E) the rejection of self cells.

E

Genetic incompatibility does not affect the
A) membrane permeability of cells.
B) growth of the pollen tube in the style.
C) attraction of a suitable insect pollinator.
D) germination of the pollen on the
stigma.
E) different individuals of the same
species.

C

What is typically the result of double
fertilization in angiosperms?
A) The endosperm develops into a diploid nutrient tissue.
B) A triploid zygote is formed.
C) Both a diploid embryo and triploid
endosperm are formed.
D) The antipodal cells develop into the seed coat.
E) Two embryos develop in every seed.

C

What is the first step in the germination of a seed?
A) fertilization
B) imbibition
C) hydrolysis of starch and other food
reserves
D) pollination
E) emergence of the radicle

B

Which of the following is an advantage of sexual reproduction as opposed to asexual reproduction?
A) increased genetic variation in progeny
B) more stable populations
C) rapid increases in population due to high seed production
D) higher reproductive success
E) enhanced mitosis

A

Under which conditions would asexual
plants have the greatest advantage over sexual plants?
A) an environment that varies on a
regular, predictable basis
B) an environment with irregular
fluctuations of conditions
C) a fire-maintained ecosystem
D) an environment with many seed
predators
E) a relatively constant environment with infrequent disturbances

E

A parent with an S1S2 genotype exhibiting sporophytic self-incompatibility can potentially fertilize which of the following plant genotypes of the same species with
pollen grains?
A) S2S3
B) S1S4
C) S1S3
D) S3S4
E) Half of all the pollen grains could be successful.

D

A parent with an S1S2 genotype exhibiting gametophytic self-incompatibility could potentially fertilize which of the following plant genotypes of the same species with
pollen grains?
A) S2S4
B) S1S4
C) S1S3
D) S2S3
E) Half of all the pollen grains could be successful.

E

Based on Figure 38.1, which cell(s), after fertilization, give(s) rise to the embryo plant?
A) A
B) B
C) C
D) D
E) E

B

Based on Figure 38.1, which cell(s) become(s) the triploid endosperm?
A) A
B) B
C) C
D) D
E) E

C

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