Exam 15: Linkage and Chromosomes

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

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

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

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)?

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

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?

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?

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?

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 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?

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?

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

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 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 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?

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

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 recombination frequency of 50% indicates ________.

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?

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?