The following figure represents a Drosophila linkage map for genes A-E. The numbers between the gene loci are the relative map units between each gene.

Figure 13.16

Based on the linkage map, which two genes are most likely to segregate together?

1. A and B
2. B and C
3. C and D
4. D and E

A test cross was made between true-breeding EEWW flies and eeww flies. The resulting F₁ generation was then crossed with eeww flies. One hundred offspring in the F₂ generation were examined, and it was discovered that the E and W genes were not linked. Which is the correct genotype of the F₂ offspring if the genes were linked and if the genes were not linked?

1. linked: 50 percent EEWW and 50 percent eeww; not linked: 25 percent EeWw, 25 percent , Eeww 25 percent eeWw, and 25 percent eeww
2. linked: 25 percent Eeww, 50 percent eeWw; not linked: parental genotypes EeWw and eeww
3. linked: genotypes EeWw and eeww, and recombinant genotypes Eeww and eeWw in the F₂ generation are nearly the same irrespective of their linkage
4. linked: mostly with parental genotypes, Eeww and eeWw; unlinked: 25 percent EeWw and eeww with 75 percent Eeww and eeWw

A cross was made with true-breeding AABB flies and true-breeding aabb flies. The resulting F1 generation then was crossed with true-breeding aabb flies. Based on the linkage map, which F2 generation genotype ratio is most likely to be observed?

Figure 13.17

A cross was made with true-breeding AABB flies and true-breeding aabb flies. The resulting F₁ generation was then crossed with true-breeding aabb flies. Based on the linkage map, which of the following F₂ generation genotype ratios is most likely to be observed?

1. number observed: AaBb (46), Aabb (4), aaBb (4), Aabb (46)
2. number observed: AaBb (4), Aabb (46), aaBb (46), Aabb (4)
3. number observed: AaBb (25), Aabb (25), aaBb (25), Aabb (25)
4. number observed: AaBb (50), Aabb (0), aaBb (0), Aabb (50)

Which symptom is most likely associated with the disorder shown in the karyotype?

1. lethality
2. infertility
3. heart and bleeding defects
4. short stature and stunted growth

Which option describes the disorder shown in the karyotype and the social, ethical, or medical issue related to the disorder?

Figure 13.18

1. Down syndrome (47 XY +21) causes intellectual disability, vision problems, congenital heart disease, and susceptibility to cancer. Healthcare providers often do not discuss the positive aspects of raising a child with Down syndrome and often provide out-of-date information.
2. Klinefelter syndrome (47 XXY) causes intellectual disability, vision problems, congenital heart disease, and susceptibility to cancer. Arguments are often made against abortion of an affected fetus.
3. Klinefelter syndrome (47 XXY) causes sterility and reduced testosterone production. Arguments are often made against informing insurance companies about a diagnosis of this disease.
4. Down syndrome (47 XY +21) causes sterility and lower testosterone production. Arguments are often made against informing insurance companies about a diagnosis of this disease.

Which gene order is the most likely outcome of an inversion mutation in the chromosome shown?

1. RSTUV
2. RRSTUV
3. RSUV
4. RTSUV

With the help of the diagram given, which statement most appropriately describes nondisjunction and its genetic consequences?

Figure 13.19

1. Nondisjunction occurs when a homologous pair is unable to separate during meiosis I, resulting in the formation of gametes containing n+1 and n-1 chromosomes. This is called aneuploidy.
2. Nondisjunction occurs due to the inability of sister chromatids to separate during meiosis II, resulting in the formation of gametes containing n+1 and n-1 chromosomes. This results in heart and bleeding defects.
3. Nondisjunction is the failure of homologous chromosomes to separate during meiosis I or failure of sister chromatids to separate during meiosis II. This results in aneuploid gametes.
4. Nondisjunction occurs when a pair of homologous chromosomes fails to segregate during meiosis II resulting in the formation of gametes containing n+1, n-1, or n numbers of chromosomes. This results in abnormal growth patterns.

Klinefelter syndrome is —

1. more severe than Down syndrome, due to gene deletions in this syndrome
2. more severe than Down syndrome, due to trisomy in Klinefelter syndrome
3. less severe than Down syndrome, due to monosomy in Down syndrome
4. less severe than Down syndrome, due to X-inactivation in this disorder