Chapter 5: Problem 22
What does the apparent need for dosage compensation mechanisms suggest about the expression of genetic information in normal diploid individuals?
Chapter 5: Problem 22
What does the apparent need for dosage compensation mechanisms suggest about the expression of genetic information in normal diploid individuals?
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Get started for freeDescribe the major difference between sex determination in Drosophila and in humans.
In mice, the Sry gene (see Section 5.2) 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 an Sry-containing piece of the Y chromosome attached to one X chromosome).
How do mammals, including humans, solve the "dosage problem" caused by the presence of an \(\mathrm{X}\) and \(\mathrm{Y}\) chromosome in one sex and two X chromosomes in the other sex?
Review the Chapter Concepts list on p. \(83 .\) These all center on sex determination or the expression of genes encoded on sex chromosomes. Write a short essay that discusses sex chromosomes as they contrast with autosomes.
In this chapter, we have focused on sex differentiation, sex chromosomes, and genetic mechanisms involved in sex determination. At the same time, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, you should answer the following fundamental questions: (a) How do we know that in humans the X chromosomes play no role in sex determination, while the Y chromosome causes maleness and its absence causes femaleness? (b) How did we originally (in the late 1940 s) analyze the sex ratio at conception in humans, and how has our approach to studying this issue changed in \(2015 ?\) (c) How do we know that X chromosomal inactivation of either the paternal or maternal homolog is a random event during early development in mammalian females? (d) How do we know that Drosophila utilizes a different sexdetermination mechanism than mammals, even though it has the same sex-chromosome compositions in males and females?
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