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A man with normal vision who is a dwarf due to achondroplasia has children with a woman who is colorblind and of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their sons are expected to be color blind and of normal height?


A) 0
B) 1/2
C) 1/4
D) all

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Use the following information to answer the question. Use the following information to answer the question.   In a Drosophila experiment, a homozygous wild-type female was crossed with a yellow-bodied male. All of the resulting F1 flies were phenotypically wild type. Crossing the F1 flies resulted in F2 flies having the characteristics shown in the figure. Which of the following statements best describes the yellow body allele? A)  It is recessive. B)  It is codominant. C)  It is dominant. D)  It is incompletely dominant. In a Drosophila experiment, a homozygous wild-type female was crossed with a yellow-bodied male. All of the resulting F1 flies were phenotypically wild type. Crossing the F1 flies resulted in F2 flies having the characteristics shown in the figure. Which of the following statements best describes the yellow body allele?


A) It is recessive.
B) It is codominant.
C) It is dominant.
D) It is incompletely dominant.

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The chromosomal alteration that results from a chromosome fragment joined to a nonhomologous chromosome is called a ________.


A) deletion
B) inversion
C) translocation
D) duplication

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C

Which of the following events results in X-inactivation in female mammals?


A) activation of the XIST gene on the X chromosome that will become the Barr body
B) activation of the BARR gene on one X chromosome, which then becomes inactive
C) inactivation of the XIST gene on the X chromosome derived from the male parent
D) attachment of methyl (-CH3) groups to the X chromosome that will remain active

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In Drosophila melanogaster, wing-size and body-color genes are linked. Vestigial wings and black body color are both recessive traits. A researcher crossed black-bodied, normal-winged females and gray-bodied, vestigial-winged males. The F1 were all gray bodied, normal winged. A test cross was performed with F1 females. The researcher calculated a map distance of 17 map units. Which of the following information is correct about the testcross progeny?


A) black-bodied, normal-winged flies = 17% of the total
B) black-bodied, normal-winged flies plus gray-bodied, vestigial-winged flies = 17% of the total
C) gray-bodied, normal-winged flies plus black-bodied, vestigial-winged flies = 17% of the total
D) black-bodied, vestigial-winged flies = 17% of the total

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A recombination frequency of 50% indicates ________.


A) the two genes are likely to be located on different chromosomes
B) all of the offspring have combinations of traits that match one of the two parents
C) the genes are located on sex chromosomes
D) the two genes are five map units apart

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Which of the following events will result in recombination between linked genes?


A) Nonhomologous chromosomes breaking and then rejoining with one another.
B) Incomplete independent assortment.
C) Linked genes traveling together at anaphase.
D) Crossovers between genes resulting in chromosomal exchange.

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D

Cinnabar eye color is an X-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a male having wild-type, red eyes, what percent of the F1 males will have cinnabar eyes?


A) 0%
B) 25%
C) 50%
D) 100%

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A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind has children with a color-blind male. What is the probability that this couple's first son will be color blind?


A) 1/4
B) 1/2
C) 2/3
D) 3/4

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Which of the following statements describes the most likely result of a defect in meiosis that results in the failure of spindle microtubules to bind some kinetochores?


A) New microtubules with more effective binding capabilities to kinetochores will be synthesized to compensate for the defect.
B) Excessive cell divisions will occur resulting an increase in the chromosome number known as polyploidy.
C) The defect will be bypassed in order to ensure normal chromosome distribution in the new cells.
D) The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy.

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Some snail species' shells can have right-handed direction of shell coiling or left-handed direction of shell coiling. The direction of coiling depends on a protein deposited by the mother in the egg cytoplasm with DD and Dd mothers depositing a protein that directs right-handed direction of coiling in shells. If Dd egg-producing snail and a dd sperm-producing snail mate what genotype(s) and phenotype(s) of offspring will result?


A) 1/2 Dd:1/2 dd; all right-coiling
B) all Dd; all right-coiling
C) 1/2 Dd: 1/2 dd; half right-coiling and half left-coiling
D) all Dd; half right-coiling and half left-coiling

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Which of the following statements explains the observation that closely linked genes are typically inherited together?


A) The genes are located close together on the same chromosome.
B) The genes undergo nondisjunction in either meiosis I or meiosis II.
C) Alleles are paired together during meiosis.
D) Crossing over between identical copies can't be detected because it regenerates the original genotype.

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Use the following information to answer the question. A plantlike species on the hypothetical planet Pandora has three genetic traits: leaf color, controlled by gene L; a stem texture, controlled by gene S; and root length controlled by gene R. Each of the three genes has two alleles. The three genes are linked and recombine. A geneticist performed a testcross with an organism of that species that is heterozygous for the three traits. She recorded progeny with the following phenotypic distribution: Use the following information to answer the question. A plantlike species on the hypothetical planet Pandora has three genetic traits: leaf color, controlled by gene L; a stem texture, controlled by gene S; and root length controlled by gene R. Each of the three genes has two alleles. The three genes are linked and recombine. A geneticist performed a testcross with an organism of that species that is heterozygous for the three traits. She recorded progeny with the following phenotypic distribution:   Assuming that genetic inheritance for this hypothetical plant functions the same as on Earth, the parents in this cross most likely have the same phenotypes as which of the following progeny? A)  2 and 5 B)  1 and 6 C)  4 and 8 D)  3 and 7 Assuming that genetic inheritance for this hypothetical plant functions the same as on Earth, the parents in this cross most likely have the same phenotypes as which of the following progeny?


A) 2 and 5
B) 1 and 6
C) 4 and 8
D) 3 and 7

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Which of the following reasons explains why map units on a chromosome linkage map are not reliable measures of physical distances?


A) The frequency of crossing over varies along the length of the chromosome.
B) The relationship between recombination frequency and map units is different in every individual.
C) Physical distances between genes change during the course of the cell cycle.
D) The gene order on the chromosomes is slightly different in every individual.

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A

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as an X-linked recessive allele in humans. A woman whose father had G6PD is planning a family with a man who has no history of the disease. What proportion of their sons are expected to have the disease?


A) 100%
B) 1/4
C) 1/2
D) 0

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In cats, an X-linked locus is responsible for fur color. There are two known alleles at this locus. One results in black fur color; the other results in orange fur color. A heterozygote animal has patches of orange and black fur (tortoiseshell) . Which coat color phenotypes are expected from the cross of a black female and an orange male?


A) tortoiseshell females; tortoiseshell males
B) black females; orange males
C) tortoiseshell females; black males
D) orange females; black males

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A testcross performed with F1 dihybrid flies results in more parental-type offspring than recombinant-type offspring. Which of the following statements best explains this result?


A) The two genes are linked on the same chromosome.
B) The two genes are linked but on different chromosomes.
C) Recombination did not occur in the cell during meiosis.
D) Both of the characters are controlled by more than one gene.

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Which of the following phrases correctly defines one genetic map unit?


A) the physical distance between any two linked genes
B) the physical distance between two genes that results in a 1% frequency of recombination
C) one nanometer of distance between two genes
D) the recombination frequency between two independently assorting genes

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A man with normal vision who is a dwarf due to achondroplasia has children with a woman with colorblindness who is of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their daughters are expected to be color-blind with achondroplasia?


A) 0
B) 1/2
C) 1/4
D) 3/4

Correct Answer

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If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n) ?


A) n + 1; n + 1; n - 1; n - 1
B) n + 1; n - 1; n; n
C) n + 1; n - 1; n - 1; n - 1
D) n + 1; n + 1; n; n

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