The genes encoding the red- and green-color-detecting proteins of the human eye are located next to one another on the X chromosome and probably evolved from a common ancestral pigment gene. The two proteins demonstrate 76 percent homology in their amino acid sequences. A normal-visioned woman (with both genes present on each of her two X chromosomes) has a red color-blind son who was shown to have one copy of the green-detecting gene and no copies of the red-detecting gene. Devise an explanation for these observations at the chromosomal level (involving meiosis).

After salivary gland cells from Drosophila are isolated and cultured in the presence of radioactive thymidylic acid, autoradiography is performed, revealing polytene chromosomes. Predict the distribution of the grains along the chromosomes.

CC (Carbon Copy), the first cat produced from a clone, was created from an ovarian cell taken from her genetic donor, Rainbow, a calico cat. The diploid nucleus from the cell was extracted and then injected into an enucleated egg. The resulting zygote was then allowed to develop in a petri dish, and the cloned embryo was implanted in the uterus of a surrogate mother cat, who gave birth to CC. CC's surrogate mother was a tabby (see the photo on page $221$ at the end of this chapter). Geneticists were very interested in the outcome of cloning a calico cat because they were not certain if the cat would have patches of orange and black, just orange, or just black. Taking into account the Lyon hypothesis, explain the basis of the uncertainty. Would you expect CC to appear identical to Rainbow? Explain why or why not.

Campomelic dysplasia (CMD1) is a congenital human syndrome featuring malformation of bone and cartilage. It is caused by an autosomal dominant mutation of a gene located on chromosome $17$. Consider the following observations in sequence, and in each case, draw whatever appropriate conclusions are warranted.
(a) Of those with the syndrome who are karyotypic $46, \mathrm{XY}$, approximately 75 percent are sex-reversed, exhibiting a wide range of female characteristics.
(b) The nonmutant form of the gene, called SOXY, is expressed in the developing gonad of the $X Y$ male, but not the $X X$ female.
(c) The SOX9 gene shares 71 percent amino acid coding sequence homology with the Y-linked $S R Y$ gene.
(d) CMD1 patients who exhibit a $46, X X$ karyotype develop as females, with no gonadal abnormalities.

In mice, the Sry gene is located on the Y chromosome very close to one of the pseudoautosomal regions that pairs with the X chromosome during male meiosis. Given this information, propose a model to explain the generation of unusual males who have two X chromosomes (with a Sry-containing piece of the Y chromosome attached to one X chromosome).

Write a balanced equation for each of the following nuclear reactions: (a) the production of $^{17} \mathrm{O}$ from $^{14} \mathrm{N}$ by $\alpha$ particle bombardment (b) the production of $^{14} \mathrm{C}$ from $^{14} \mathrm{N}$ by neutron bombardment (c) the production of $^{233} \mathrm{Th}$ from $^{232} \mathrm{Th}$ by neutron bombardment (d) the production of $^{239} \mathrm{U}$ from $^{238} \mathrm{U}$ by $_{1}^{2} \mathrm{H}$ bombardment

Devise as many hypotheses as you can that might explain why so many more human male conceptions than human female conceptions occur.

Contrast the life cycle of a plant such as Zea mays with an animal such as $C$. elegant.

What type of evidence supports the conclusion that the primary sex ratio in humans is as high as 1.20 to 1.60?

How does X chromosome dosage compensation in Drosophila differ from that process in humans?

What does the apparent need for dosage compensation mechanisms suggest about the expression of genetic information in normal diploid individuals?

What specific observations (evidence) support the conclusions about sex determination in Drosophila and humans?

Cat breeders are aware that kittens expressing the X-linked calico coat pattern and tortoiseshell pattern are almost invariably females. Why are they certain of this?

A solid is generated by revolving the region bounded by y = ½x² and y = 2 about the y-axis. A hole, centered along the axis of revolution, is drilled through this solid so that one-fourth of the volume is removed. Find the diameter of the hole.