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Biology Genetics 1-4 chapters

Terms in this set (42)

Which of the following statements is false?

a. Errors in chromosome separation are rarely a problem for an organism.

b. Errors in chromosome separation can result in a child with severe handicaps.

c. Errors in chromosome separation can cause numerous problems for an organism.

d. Errors in chromosome separation can result in cancer.

e. Errors in chromosome separation can result in a miscarriage.
a. Errors in chromosome separation are rarely a problem for an organism.
Which of the following statements is false?

a. Eukaryote chromosomes are usually linear.

b. Generally, chromosomes of eukaryotes are circular.

c. Eukaryotes usually have multiple chromosomes.

d. Prokaryotes usually have a single molecule of DNA.

e. Generally, chromosomes of prokaryotes are circular.
b. Generally, chromosomes of eukaryotes are circular.
The centromere divides a chromosome into two sections or "arms." A chromosome is found to have two arms of equal lengths. Such a chromosome can be BEST described as:

a. homologous.
b. telocentric.
c. metacentric.
d. acrocentric.
c. metacentric.
A dividing eukaryotic cell is treated with a drug that inhibits the molecular motors associated with kinetochores. At which cell cycle stage would it stop?

a. G1
b. M (telophase)
c. M (metaphase)
d. S
c. M (metaphase)
Why is mitosis important within the cell cycle?
Mitosis is important because it results in two daughter cells that have identical nuclear chromosome complements so the daughter cells are genetically identical to each other and genetically identical to the parent cell from which they arose.
Explain why mitosis does not produce genetic variation and how meiosis leads to the production of tremendous genetic variation.
Mitosis produces cells that are genetically identical to the parent cell. Meiosis includes two distinct processes that contribute to the generation of genetic variation: Crossing over shuffles alleles on the same chromosome into new combinations, whereas the random distribution of pairs of homologous chromosomes, one member of each pair coming from the mother and the other from the father, shuffles alleles on different chromosomes into new combinations.
List and briefly describe three major cell cycle checkpoints. For each checkpoint, predict the consequences if the checkpoint fails to work properly.
(1) The G1/S checkpoint holds the cell in G1 until the cell has all of the enzymesnecessary for replication of DNA. If the checkpoint failed, the cell would proceed into S without the necessary enzymes, causing the DNA not to be replicated properly or completely. This might cause the cell cycle to halt at the G2/M checkpoint. Alternatively, the cell might divide without the genetic material having been replicated, causing the daughter cells to receive incomplete genetic information. Both predictions are reasonable based on information in the chapter.(2) The G2/M checkpoint is passed only if the cell's DNA is undamaged. If it fails to work properly, division would proceed in the presence of damaged DNA, possibly leading to mutations in the daughter cells and/or death of the daughter cells.(3) The spindle-assembly checkpoint is during metaphase, and it ensures that each chromosome is aligned at the metaphase plate and attached to spindle fibers from opposite poles. This checkpoint depends on tension at the kinetochores of each chromosome. If the checkpoint fails, anaphase will occur even when the chromosomes are not aligned properly, allowing daughter cells to be produced with extra and/or missing chromosomes.
A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of telomeres in a rat cell in G2?

a. 21
b. 84
c. 168
d. 42
c. 168
What might be the result if the breakdown of the shugoshin protein were premature?

a. The separation of homologous chromosomes would occur prematurely.

b. The cohesion protein would hold the chromosome arms together longer.

c. Spindle fibers would not form

d. The separation of sister chromatids would occur prematurely.
a. The separation of sister chromatids would occur prematurely.
Chromosome movement during anaphase is a result of

a. the cohesion protein attaching to the centromeres of sister chromatids.

b. metaphasal plate splitting resulting in chromosomal disassembly.

c. kinetochore shortening causing chromosomes to pull apart.

d. cilia movement inside the cellular structure.

e. disassembly of tubulin molecules by molecular motor proteins.
e. disassembly of tubulin molecules by molecular motor proteins.
Freckles are caused by a dominant allele. A man has freckles but one of his parents does not have freckles. What is the man's genotype?

a. homozygous dominant

b. heterozygous

c. heterologous

d. homologous
b. heterozygous
In a cross between AABbCcDD and AaBbccdd, what proportion of the offspring would be expected to be A_B_C_D_? (A_ means AA or Aa.)

a. 3/256
b. 3/16
c. 3/8
d. 3/4
c. 3/8
Gregor Mendel carried out a cross between two pea plants by taking pollen from a plant that was homozygous for round seeds and dusting the pollen onto the stigma of a plant homozygous for wrinkled seeds. Which of the following would be the reciprocal cross that Mendel had carried out for this experiment?

a. Stigma of a plant homozygous for wrinkled seed pollinated with pollen from a plant homozygous for round-seed plant

b. Stigma of a plant heterozygous for round seed pollinated with pollen from a plant homozygous for wrinkled-seed plant

c. Stigma of a plant homozygous for round seed pollinated with pollen from a plant homozygous for wrinkled-seed plant

d. Stigma of a plant homozygous for round seed pollinated with pollen from a plant heterozygous for wrinkled-seed plant
c. Stigma of a plant homozygous for round seed pollinated with pollen from a plant homozygous for wrinkled-seed plant
In Labrador retrievers, black coat color is dominant to brown. Suppose that a black Lab is mated with a brown one and the offspring are four black puppies and one brown puppy. What can you conclude about the genotype of the black parent?

a. The genotype must be Bb.

b. The genotype must be bb.

c. The genotype must be BB.

d. The genotype could be either BB or Bb.
a. The genotype must be Bb.
In Mendel's peas, purple flower color is dominant to white. From which of the following descriptions can you NOT infer the genotype completely?

a. purple

b. pure-breeding purple

c. pure-breeding white

d. white
a. purple
Which of the following crosses would produce a 1:1 ratio of phenotypes in the next generation?

a. Aa × aa
b. AA × AA
c. Aa × Aa
d. AA × aa
a. Aa × aa
Which of the following crosses would produce a 3:1 ratio of phenotypes in the next generation?

a. Aa × Aa
b. AA × aa
c. Aa × aa
d. AA × AA
a. Aa × Aa
In animals, the inability to make the pigment melanin results in albinism, a recessive condition. Two unaffected parents, who have decided to have three children, have a first child that has albinism (genotype aa). What is the probability that the second and third children will also have albinism?

a. 1/4
b. 1/16
b. 1/2
c. 9/16
b. 1/16
Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a wrinkled, green seed in the F2?

a. 9/16
b. 1/16
c. 3/4
d. 3/16
b. 1/16
Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a yellow seed in the F2?

a. 1/16
b. 3/4
c. 9/16
d. 3/16
b. 3/4
Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A plant of unknown genotype is testcrossed to a true-breeding plant with wrinkled and green seeds. The offspring produced were 53 round and yellow, 49 round and green, 44 wrinkled and yellow, and 51 wrinkled and green. What is the likely genotype of the parent in question?

a. RRYy
b. RRYY
c. RrYY
d. RrYy
d. RrYy
A man has either an AaBB or AABb genotype with equal probability. Assume these genes assort independently. What is the overall probability that the man will produce an Ab gamete?
show work
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AB gamete from an AaBb individual?

a. 1/16
b. 9/16
c. 1/4
d. 1
e. 1/2
c. 1/4
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AB gamete from an AABb individual?

a. 1/2
b. 1/4
c. 9/16
d. 1/16
e. 1
a. 1/2
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AABB zygote from a cross of AaBb × AaBb?

a. 9/16
b. 1/16
c. 1/4
d. 1
e. 1/2
b. 1/16
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AaBb zygote from a cross of AaBb × AABB?

a. 1/2
b. 9/16
c. 1/4
d. 1
e. 1/16
c. 1/4
Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an offspring with the AB phenotype from a cross of aabb × AABB?

a. 1/4
b. 1/2
c. 1
d. 1/16
e. 9/16
c. 1
What is the role of the SRY gene in humans?

a. It is located on the X chromosome and causes the X to pair with the Y chromosome during male meiosis.

b. It is located on an autosomal chromosome and represses expression of autosomal genes in order to balance their expression level with genes on the X chromosome.

c. It initiates the X inactivation process in females.

d. It is located on the Y chromosome and initiates the developmental pathway toward the male phenotype.
d. It is located on the Y chromosome and initiates the developmental pathway toward the male phenotype.
What is the expected outcome for a human embryo with the XXXY chromosome constitution?

a. It would likely develop into a tall female who may be slightly cognitively impaired.

b. It would likely develop into a sterile male with reduced testes.

c. It will always abort early in development before birth.

d. It would likely develop into a female who will not respond to the hormone testosterone.
b. It would likely develop into a sterile male with reduced testes.
Which of the following chromosome constitutions would never lead to a viable human baby being born?

a. XYY
b. XO (O = the absence of a second chromosome)
c. YY
d. XXX
c. YY
In which of the following organisms is gender/sex determined by the temperature during embryonic development?

a. many snakes and birds
b. fruit flies
c. mice
d. many turtles and alligators
d. many turtles and alligators
An XXY chromosome constitution produces _____ development in humans and _____ development in fruit flies.

a. male, female
b. female; male
c. male; male
d. female; female
a. male, female
Human females with XY chromosomes and a phenotype that includes the absence of a uterus and ovaries and the presence of testes are likely to have which of the following mutations?

a. They likely do not carry a mutation but may have been premature babies.

b. a deletion that removes much of the Y chromosome

c. a mutation in the SRY gene

d. a mutation in the androgen receptor gene
d. a mutation in the androgen receptor gene
Explain the genders of human and diploid Drosophila XXY individuals.
An XXY human is male. The SRY on the Y chromosome determines maleness, in spite of the two X chromosomes. An XXY Drosophila is female. Drosophila is diploid, so there are two of each autosome. If there are two X chromosomes, the X:A ratio is 1.0, which is a female.
Suppose that an apparently female athlete fails a gender test and is not allowed to compete in her event. The gender test is based on examination of cheek cells for the presence of one or more Barr bodies. Later, it is discovered that the athlete has androgen-insensitivity syndrome. Explain why the athlete failed the gender test. What did the technician see in the test and how was it interpreted?
Because the athlete is XY, the technician would have seen no Barr bodies in her cells. The absence of Barr bodies is normally characteristic of males, so the test was interpreted to indicate that the athlete is genetically male.
Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision. Which phenotype is NOT expected?

a. a color-blind female
b. a noncolor-blind female
c. a color-blind male
d. a noncolor-blind male
a. a color-blind female
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the mutant phenotype?

a. 0%
b. 100%
c. 33%
d. 25%
a. 0%
Michael is a 42-year-old man with hemophilia, a sex-linked recessive condition. His daughter, Emily, who has normal blood clotting, is married to Jack who also has hemophilia. Emily and Jack are expecting their first child and an ultrasound shows that the fetus is male. What is the approximate probability that their new son will have hemophilia?

a. 2/3
b. 1
c. 3/4
d. 1/4
e. 1/2
e. 1/2
Which of the following statements about the sex-linked recessive trait of red-green color blindness in humans is FALSE?

a. A color-blind daughter can have a phenotypically normal mother.
b. A color-blind daughter can have a normal father.
c. A phenotypically normal daughter can have a color-blind mother.
d. A color-blind son could have a color-blind father.
e. A phenotypically normal daughter can have a color-blind father.
b. A color-blind daughter can have a normal father
You cross a female rat with pink toe pads (T) and pointy ears (Xe) to a male rat with black toe pads (t) and round ears (XE). The t and e alleles are both recessive, and the ear-shaped gene is X linked, whereas the toe pad color gene is autosomal. The F1 progeny all have pink toe pads. What is the genotype of parental generation? What is the genotype of the F1 progeny? If the F1 are crossed to produce F2 progeny, what proportion of the F2 will be black-padded, pointy-eared males?
The parental generation was T/T; Xe/Xe and t/t; XE/Y. The F1 were T/t; XEXe and T/t;XeY. Black-padded, pointy-eared males are tt and Xe/Xe. One-quarter of the F2 progeny will be t/t, ¼ will be XeY. Therefore, 1/16 of the progeny will be black-padded, pointy-eared males.
What is the apparent purpose for X inactivation in humans and other mammals?

a. It allows for the levels of expression of genes on the autosomes to be similar to the levels of genes on the X chromosome.

b. It enhances the level of pairing between the two X chromosomes during meiosis in females.

c. It reduces the amount of nondisjunction during meiosis in females.

d. It allows for the levels of expression of genes on the X chromosome to be similar in males and females.

e. It suppresses the expression of genes on the Y chromosome in males.
d. It allows for the levels of expression of genes on the X chromosome to be similar in males and females.
In which of the following individuals would you expect to find two Barr bodies in their somatic cells?a.b. XOc.d. e.

a. XXY
b. XXX
c. XX
d. XXYY
b. XXX
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