Practice Final Exam 102

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Round pea shape is dominant over wrinkled pea shape. If a round pea has a wrinkled parent, the
round pea is:

Rr

Autosomal nondisjunction can result in:

Down syndrome.

In humans, the sex of the offspring is determined by the:

sex chromosome carried by the sperm cell.

All of the following statements about genotypes and phenotypes are true EXCEPT:

matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes.

If two parents are carriers of albinism (an autosomal recessive trait), what is the chance that their
fourth child will have a homozygous genotype?

50%

Based on this pedigree, which individual was a carrier for hemophilia but did not suffer from the
disease?

Irene

Imagine that smurfs live in widely separated groups and rarely interbreed, so geneticists know
very little about them. On one occasion, two smurfs from different groups did mate. A big-footed,
white smurf mated with a small-footed, blue smurf. Three offspring resulted: one big-footed and
blue and two small-footed and blue.Which statement about the inheritance of color in smurfs is
most likely to be correct?

Blue is dominant to white.

Which disorder is characterized by an abnormal number of autosomes?

Down syndrome

Traits controlled by sex-linked recessive genes are expressed more often in males because:

the male has only one gene for the trait.

When Mendel used true-breeding white flowers and true-breeding purple flowers as the parental
generation, what were the results? (Purple flower is dominant over white.)

All the offspring had purple flowers.

Two people with normal vision have two sons, one color blind and one with normal vision. If this
couple then has six daughters, what percentage of the daughters should have normal color vision?

100%

What type of allele produces its effects in only homozygous individuals?

recessive

A sex-linked recessive condition that causes abnormal color vision is called

color blindness.

A pea plant with red flowers is test crossed; half of the resulting progeny have red flowers, while
the other half have white flowers. The genotype of the test crossed parent was:

Rr

A human sperm cell possesses autosomes and:

either an X or a Y chromosome.

Which disorder is more common among the babies of older mothers?

Down syndrome

Human skin color is the result of:

polygenic inheritance.

In Mendel's experiments, if the gene for tall (T1) plants was incompletely dominant over the gene
for short (T2) plants, what would be the result of crossing two T1T2 plants?

25% tall, 50% intermediate, and 25% short

Human eye color is the result of:

polygenic inheritance.

Blood typing is often used as evidence in paternity cases in court. In one case, the mother had blood
type B and the child had blood type O. Which of the following blood types could the father NOT
have?

AB

In a test cross, what percentage of the offspring will have the same phenotype as the tested parent if
the parent to be tested is homozygous?

100%

In crossing a homozygous recessive with a heterozygote, what is the chance of getting a
homozygous recessive phenotype in the F1 generation?

50%

Gregor Mendel concluded that each pea has two units for each trait, and each gamete contains one
unit. Mendel's "units" are now called:

genes.

A recessive allele on the X chromosome causes color blindness. A noncolor-blind woman (whose
father is color blind) marries a color-blind man. What is the chance that their son will be color
blind?

50%

Suppose you cross a pea plant with yellow, smooth seeds with one that has wrinkled, green seeds.
You examine the seeds of 967 offspring and find that some have yellow, smooth seeds and some
have yellow, wrinkled seeds, but no green seeds of either type show up. What is the genotype of
the yellow-seeded parent? (Y = yellow, y = green; S = smooth, s = wrinkled)

YYSs

When the two gametes that fuse to form a zygote contain different alleles of a given gene, the
offspring is:

heterozygous.

For a eukaryotic chromosome, which of the following is true?

RNA chains of different genes can be transcribed from either DNA strand, but the growing
RNA strand always starts at the 5' end and moves toward the 3' end.

The process of copying genetic information from DNA to RNA is called:

transcription.

Which of the following occurs in the nucleus?

both transcription and replication of genetic material

What does mRNA carry away from the nucleus?

information

Ribosomes are a collection of:

proteins and small RNAs that function in translation.

Which of the following is made up of amino acids?

RNA polymerase

Which of the following elongates RNA molecules in the nucleus?

RNA polymerase

The sequence of nitrogen-containing bases on one strand of DNA most directly determines the
sequence of:

amino acids in a protein molecule.

Which point mutation would be most likely to have a catastrophic effect?

a base deletion near the start of the coding sequence

How can a single gene code for more than one protein?

The exons within a mRNA can be spliced together in different ways.

Which of the following contains four types of nucleotides but no uracil?

DNA

Suppose one strand of a "mini-gene" has the base sequence TACCCGGATTCA. If we assume no
introns are involved, how many amino acids does the polypeptide encoded by this gene have?

4

Which of the following contains codons?

messenger RNA

What is the anticodon for AUC?

UAG

A sequence of three RNA bases can function as a(n):

anticodon only.

The genetic material of some viruses, such as HIV, is not normal DNA but is instead:

RNA

Imagine that the short DNA base sequence GGCTGC is transcribed and then translated by a
ribosome. The following activated tRNA molecules are available in the cytoplasm:
What resulting dipeptide will form?

proline-threonine

A "mini-gene" has the base sequence TACCCGTGCACG. Which of the following sequences
represents a single base substitution?

TACCCGAGCACG

A tRNA that carries a specific amino acid enters the protein-synthesizing machinery at the
ribosomes and pairs with the appropriate:

codon.

Both DNA and RNA:

contain phosphate groups.

Which of the following is NOT a means of regulating gene expression?

deleting genes from cells in which they are not needed

Which of the following is noted when comparing DNA and RNA?

Adenine pairs with different bases in DNA and RNA.

What is the site of protein synthesis?

ribosome

Fish in a local lake have a mixture of brown and green scales and are found throughout the lake.
Over a five-year period, the lake develops more plant growth and an exotic predatory frog is introduced. What change would you expect to see in the original fish population?

The fish with green scales will become more common.

The human appendix is an example of a(n):

vestigial structure.

Which of the four postulates of Darwin's theory of evolution was not well established when On the
Origin of Species was first published but is overwhelmingly supported today?

Some differences among individuals in a population are due to genetics and are heritable.

Convergent evolution occurs when:

unrelated organisms develop analogous structures.

Charles Darwin believed that artificial selection was:

similar in many ways to natural selection.

Sea squirts and lampreys, which are both aquatic animals, have a perforated pharynx, a ventral
heart, and a notochord at some stage of development. These similarities are BEST explained by:

a common ancestry.

A farmer noticed that two of her cotton plants produce cotton with a slight greenish hue. By
repeatedly crossing the greenish plants, she has produced a variety of deep-green cotton without
the use of any dyes. This is an example of:

artificial selection.

The publication date of On the Origin of Species by Means of Natural Selection was:

1859.

The amino acid sequences of human and chimpanzee hemoglobin are almost identical, yet they
differ considerably from the sequence of the hemoglobin of dogs. This fact:

supports the theory of evolution.

If the weather in Virginia changed so dramatically that there was snow on the ground most of the
year, what would occur in the local squirrel population?

If a mutation occurred that caused white fur to develop, such white squirrels would likely
survive and reproduce better than gray squirrels.

Which mutation provides a survival advantage?

a flower that attracts more bees

The controlled breeding of domestic plants and animals by humans in order to produce certain
physical traits in those organisms is called:

artificial selection.

Of all the possible amino acids, all living organisms make use of only the same 20 amino acids. This
supports the idea that:

all living things are derived from a single common ancestor.

Who wrote On the Origin of Species by Means of Natural Selection?

Darwin

Natural selection is BEST described as:

working on the existing variation of traits to favor those better suited to the organism's environment.

Dolphins (which are mammals) and sharks (which are fish) have stiff dorsal fins projecting from
their backs that help them maneuver through water. These structures are BEST described as:

homologous structures.

In one butterfly species, the colors of individuals range from white to black, with many shades of
gray in between. If the butterflies in a mountain population become more and more similar in color
over several generations (for example, if most butterflies are the same shade of gray), what kind of
evolutionary force is likely acting on the population?

stabilizing selection

Imagine that one of the original four mice that escape from a research lab is blind due to a genetic
defect. If the mice breed and most of the mice born in subsequent generations are blind from birth,
this is most likely a case of:

the founder effect.

Habitat loss, natural catastrophes, and/or excessive harvesting of a species often result in:

population bottlenecks.

The process by which allele frequencies are altered in a population to improve the odds of
attracting a mate is called:

sexual selection.

A population carries two alleles for a trait in which T is dominant and t is recessive. In the
Hardy-Weinberg equation, 2pq represents:

the proportion of heterozygous individuals.

A population is defined as:

all individuals of the same species located in a given geographic region.

As predator and prey species acquire new adaptations to help them survive the constant "arms
race" between them, what evolutionary phenomenon is occurring?

coevolution

The interaction of genes and environment produces a specific:

phenotype.

The type of selection most likely to act on a well-adapted population in a relatively constant
environment is:

stabilizing.

In Central Africa, the frequency of the sickle-cell allele has remained stable over the years because
the allele protects against malaria. In the United States, malaria was eradicated by eliminating the
mosquito that spreads the disease. The decreasing frequency of the sickle-cell allele in African
Americans since malaria was eliminated in the United States is an example of:

directional selection.

In the context of evolution, equilibrium means:

no change in allele frequency.

Genetic drift results in a change in gene frequencies because:

the population size is so small that chance occurrences can alter gene frequencies.

Which trait is the BEST example of an adaptation?

a mutation resulting in a heat-resistant enzyme in a bacterium living in a hot spring

Inbreeding is defined as:

sexual reproduction among closely related individuals.

Zoos often loan animals to other zoos for breeding purposes. From an evolutionary standpoint,
what is the benefit?

It increases the genetic diversity of the zoo's population.

Which of the following is an example of assortative mating?

A female mouse chooses a mate because he is the same color that she is.

Within a large population, if no mutations occur, no migration occurs, all matings are random, and
each individual has an equal chance of reproducing, which of the following will probably happen?

No evolution will occur.

When a species lives in a constant environment for a long time, the "average type" of individual
may have the best chance of surviving and producing the most offspring. What type of selection is
occurring?

stabilizing

Which species is least likely to become extinct?

a mammal species that can live equally well on dry land and in fresh water

Two species of squirrels live on either side of the Grand Canyon. It is believed that a long time ago,
before being separated by the canyon, they were the same species. This is an example of:

allopatric speciation.

A group of interbreeding natural populations that is reproductively isolated from other such
groups is a:

species.

The biological concept of species requires that:

organisms reproduce sexually.

Fruit fly species all look similar to one another. If you have a male and a female fruit fly, how can
you prove that they are the same species, according to the biological species concept?

If they mate successfully and their offspring are fertile, they are the same species.

Two species of pines, Pinus radiata and Pinus muricota, live in the same regions of California and are
capable of forming hybrids under laboratory conditions. However, they do not interbreed because
one releases pollen in February and the other in April. What genetic isolating mechanism is
involved?

temporal

Which statement BEST describes the reproductive isolation between populations of Rhagoletis flies
found on apple and hawthorn trees?

Apple-liking males are more likely to encounter apple-liking females than hawthorn-liking females.

Interbreeding two different species of lovebirds produces offspring that are unable to build a nest
after they mature because they lack the appropriate innate knowledge needed to carry the nesting
materials and build a nest. This limits genetic mixing between the species due to:

behavioral isolation.

What is the BEST explanation for the origin of the unique species recently found in the Annamite
Mountains of Vietnam?

allopatric speciation

The parasitic Rhagoletis flies that show a preference for either hawthorn or apple trees and are no
longer interbreeding populations illustrate what type of speciation?

sympatric

One method of protecting the genetic isolation of a population is the inability of sperm to fertilize
eggs of a different species. This is called:

gametic incompatibility.

Female blue-footed boobies of the Galápagos Islands will mate only after a very specific courtship
display on the part of the male. He high-steps to advertise his bright blue feet. What mechanism
discourages female blue-footed boobies from mating with other species of boobies that have
different courtship displays?

behavioral isolation

Which species is MOST likely to become extinct?

Kirtland's warbler, which breeds in only a small area of Michigan

The biological species concept cannot be applied to:

extinct organisms.

When the pollen of one plant species will not germinate on the flower of another species, it is an
example of:

gametic incompatibility.

Current research indicates that the greatest biodiversity is found in:

tropical rain forests.

Modern systematics constructs clades and evolutionary relationships based on:

genetic similarities.

A house cat has the scientific name Felis catus. The term "catus" is the:

species.

Which of the following is eukaryotic?

Fungi

If genetic studies reveal that a population has genetic sequences in common with two closely
related species but has no unique sequences of its own, then:

it should be considered a hybrid of the two species.

Why do some biologists not consider reptiles to be a monophyletic group?

Birds are the direct descendants of some reptiles.

Which of the following groups contains the fewest species?

order

Systematics reassigns phylogenetic placement based on:

new information about genetic relationships

What should biologists do when two similar organisms that were originally thought to be separate
species are found to interbreed freely and produce normal offspring whenever they live in the same
habitat?

Consider both types to be a single species.

Evolutionary relationships among organisms are most likely to be revised at the ________ level.

species

Which of the following is eukaryotic?

humans.

Based on evolutionary lineage, fungus and animals belong to the same:

clade.

The physical manifestation of an organism's genes is its:

phenotype.

When genes are linked, a few of the recombinant genotypes still occur in the offspring because of:

crossing over.

If, in a heterozygous individual, only one allele is expressed in the phenotype, that allele is:

dominant.

All of the following combinations are possible in the gametes of an organism that is AaBb EXCEPT:

aa

A man who carries a harmful sex-linked (on the X chromosome) gene will pass the gene on to:

all of his daughters.

A type of muscular dystrophy shows sex-linked recessive inheritance. Affected persons usually die
by the age of 20. Suppose that a boy with the disease lives long enough to marry a woman
heterozygous for the trait. If they have a son, what is the probability that he will have the disease?

50%

What is the genotype of a dominant individual if some of its offspring show the recessive
phenotype?

Dd

The failure of chromosomes to segregate properly during meiosis is called:

nondisjunction.

"Gene expression" is a term that relates to:

the flow of genetic information from DNA to proteins.

A gene mutation is defined as change in the:

nucleotide sequence of DNA.

Which of the following attaches to specific amino acids?

transfer RNA

What kind of mutation occurs when one base is changed to another at a single location in the DNA?

substitution

For a mutation to affect the evolution of an animal species, it must occur within:

gametes.

Which of the following has the fewest nucleotides in its strand?

mRNA having 75 nucleotides.

In a wild-type strain of fruit flies, the length of a gene from the start to the stop codon is 2,000 DNA
bases. Suppose an experiment indicated that the mRNA molecule transcribed from this gene is
much shorter (only 1,200 bases). What is the most likely explanation for this?

There are introns in the DNA that were cut out of the mRNA.

How many bases are in a codon?

3

Which of the following is an excellent example of artificial selection?

the many different breeds of domestic cats

Which of the following would you expect to occur in a captive population of guppies collected
from Trinidad, if you allowed them to breed for many generations in an aquarium without any
predators?

Male guppies that are brightly colored will have better reproductive success than dull males.

Where are the Galápagos Islands?

off the west coast of South America

Evidence that supports the theory of evolution is found in the studies of:

embryos, biochemistry, fossils, and artificial selection.

Strong evidence for the common ancestry of all vertebrates is:

the similarity of their embryological stages.

Darwin realized that most species produce many more offspring than is necessary to maintain a
constant population. The "excess" individuals in a population:

die before they can reproduce.

Imagine that a biologist develops a strain of corn with a lower fat content by choosing low-fat
variants and crossbreeding them over several generations. This is an example of:

artificial selection.

Which of the following can cause evolutionary change in a small population?

genetic drift

Multidrug-resistant bacteria:

are becoming more widespread.

Suppose that the only population of a certain reptile species lives on an African mountain. If you
could prevent all movement of individuals out of this large but isolated population, which of the
following describes the most likely future of this reptile population?

Evolution will continue because of mutations, assortative mating, and genetic drift

Imagine you are studying leaf size in a large population of plants over several years. In one year of
your study there is a below-average amount of rainfall, and the following year the average leaf size
in the population is smaller than before. However, the amount of variation in leaf size is the same
and the population size doesn't change. Other scientists have done experiments showing that small
leaves are better adapted to dry conditions than large leaves. What has most likely occurred?

directional selection

In northern Minnesota, the lynx (Lynx Canadensis) habitat overlaps the bobcat (Lynx rufus) habitat.
The two can breed and produce healthy, fertile offspring, which could lead to:

extinction of one or both species.

The immediate cause of most extinctions is:

environmental change.

Before the modern era of science, organisms were assigned to species on the basis of:

similarities in appearance.

The organisms most likely to undergo sympatric speciation by polyploidy are:

plants

Since the Pleistocene ice age, deserts have been gradually forming in the southwestern United
States. As the original lakes and rivers of this area shrank into isolated streams, ponds, and springs,
the fishes living in them developed a strong potential for:

speciation.

Which of the following is the correct way to write the scientific name of the wolf?

Canis lupus (italized)

Based on the eukaryotic tree, Gymnosperms are most closely related to:

Angiosperms.

Based on the evolutionary tree shown here, which two organisms are most closely related?

chimps and bonobos

Canis latrans, Canis lupus, and Canis familiaris are all members of the same:

family and genus.

DNA analysis reveals that two species of birds appear to have evolved from a common ancestor.
These two species belong to the same:

clade.

The results of a test cross reveal that all the offspring resemble the parent being tested. This parent
must be:

homozygous.

Sickle-cell anemia is caused by a:

recessive autosomal gene.

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