Essentials of Genetics (9th Edition) - Standalone book
9th Edition
ISBN: 9780134047799
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino
Publisher: PEARSON
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Chapter 5, Problem 25PDQ
In mice, the X-linked dominant mutation Testicular feminization (Tfm) eliminates the normal response to the testicular hormone testosterone during sexual differentiation. An XY mouse bearing the Tfm allele on the X chromosome develops testes, but no further male differentiation occurs–the external genitalia of such an animal are female. From this information, what might you conclude about the role of the Tfm gene product and the X and Y chromosomes in sex determination and sexual differentiation in mammals? Can you devise an experiment, assuming you can “genetically engineer” the chromosomes of mice, to test and confirm your explanation?
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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 an Sry-containing piece of the Y chromosome attached to one X chromosome).
. Researchers discovered recently that the sole functionof the SRY protein is to activate an autosomal genecalled Sox9 in the presumptive gonad (before it has“decided” to become a testis or an ovary).a. What would be the sex of an XY individual homozygous for nonfunctional mutant alleles of Sox9?Explain.
During meiosis in male mammals, sex chromosomes segregate to produce two types of sperm: X‑bearing sperm and Y‑bearing sperm.
True or false?
Chapter 5 Solutions
Essentials of Genetics (9th Edition) - Standalone book
Ch. 5 -
CASE STUDY | Doggone it!
A dog breeder...Ch. 5 - CASE STUDY| Doggone it! A dog breeder discovers...Ch. 5 - CASE STUDY| Doggone it! A dog breeder discovers...Ch. 5 -
CASE STUDY | Doggone it!
A dog breeder...Ch. 5 - HOW DO WE KNOW? In this chapter, we have focused...Ch. 5 - Review the Chapter Concepts list on p. 84. These...Ch. 5 - As related to sex determination, what is meant by...Ch. 5 -
4. Contrast the life cycle of a plant such as...Ch. 5 - Prob. 5PDQCh. 5 -
6. Describe the major difference between sex...
Ch. 5 - How do mammals, including humans, solve the...Ch. 5 -
8. What specific observations (evidence) support...Ch. 5 - Describe how nondisjunction in human female...Ch. 5 -
10. An insect species is discovered in which the...Ch. 5 -
11. Given your answers to Problem 10, is it...Ch. 5 - When cows have twin calves of unlike sex...Ch. 5 -
13. An attached-X female fly, XXY (see the...Ch. 5 -
14. Assume that on rare occasions the attached X...Ch. 5 - It is believed that any male-determining genes...Ch. 5 -
16. What is a Barr body, and where is it found...Ch. 5 - Indicate the expected number of Barr bodies in...Ch. 5 - Define the Lyon hypothesis.Ch. 5 - Can the Lyon hypothesis be tested in a human...Ch. 5 - Predict the potential effect of the Lyon...Ch. 5 -
21. Cat breeders are aware that kittens...Ch. 5 -
22. What does the apparent need for dosage...Ch. 5 - In mice, the Sry gene (see Section 5.2) is located...Ch. 5 - The genes encoding the red- and...Ch. 5 - In mice, the X-linked dominant mutation Testicular...Ch. 5 -
26. Shown here are graphs that plot the...Ch. 5 -
27. In chickens, a key gene involved in sex...
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- In chickens, a key gene involved in sex determination has recently been identified. Called DMRT1, it is located on the Z chromosome and is absent on the W chromosome. Like SRY in humans, it is male determining. Unlike SRY in humans, however, female chickens (ZW) have a single copy while males (ZZ) have two copies of the gene. Nevertheless, it is transcribed only in the developing testis. Working in the laboratory of Andrew Sinclair (a co-discoverer of the human SRY gene), Craig Smith and colleagues were able to “knock down” expression of DMRT1 in ZZ embryos using RNA interference techniques. In such cases, the developing gonads look more like ovaries than testes [Nature 461: 267 (2009)]. What conclusions can you draw about the role that the DMRT1 gene plays in chickens in contrast to the role the SRY gene plays in humans?arrow_forwardIn chickens, a key gene involved in sex determination has recently been identified. Called DMRT1, it is located on the Z chromosome and is absent on the W chromosome. Like SRY in humans, it is male determining. Unlike SRY in humans, however, female chickens (ZW) have a single copy while males (ZZ) have two copies of the gene. Nevertheless, it is transcribed only in the developing testis. Working in the laboratory of Andrew Sinclair (a co-discoverer of the human SRY gene), Craig Smith and colleagues were able to “knock down” expression of DMRT1 in ZZ embryos using RNA interference techniques (see Chapter 18). In such cases, the developing gonads look more like ovaries than testes [Nature 461: 267 (2009)]. What conclusions can you draw about the role that the DMRT1 gene plays in chickens in contrast to the role the SRY gene plays in humans?arrow_forwardResearchers discovered recently that the sole functionof the SRY protein is to activate an autosomal genecalled Sox9 in the presumptive gonad (before it has“decided” to become a testis or an ovary).a. What would be the sex of an XY individual homozygous for nonfunctional mutant alleles of Sox9?Explain.b. Given your answer to part (a), why is SRY, ratherthan Sox9, considered the male determining factor?(Hint: What do you think would happen if you didan experiment like the one in the Fast Forward BoxTransgenic Mice Prove That SRY Is the MalenessFactor, except that you used a Sox9 transgeneinstead of SRY?)arrow_forward
- Butterflies have an X-Y sex-determination system that is different from that of flies or humans. Female butterflies may be either XY or X0, while butterflies with two or more X chromosomes are males. This photograph shows a tiger swallowtail gynandromorph, which is half male (left side) and half female (right side). Given that the first division of the zygote divides the embryo into the future right and left halves of the butterfly, propose a hypothesis that explains how nondisjunction during the first mitosis might have produced this unusual-looking butterfly. Question is also in the picture.arrow_forwardWith relevance to sex determination in humans, discuss: i) X chromosome inactivation; and ii) Testicular feminization Provide detail examples.arrow_forwardDraw a schematic diagram showing spermatogenesis vis-à-vis oogenesis. Label the stage of development and chromosome number of daughter cells at the following levels of maturation: (a) mitotic proliferation (b) meiosis I and II (c) maturation. Table 2: Spermatogenesis vis-à-vis Oogenesis Spermatogenesis Oogenesisarrow_forward
- In the process of Oogenesis in animal cells, will the genotype of the second polar body (derived from meiosis II) always be identical to that of the ootid? Why or why not?arrow_forwardExplain the consequent of each of the following on neurulation: a. Inhibition of microtubules polymerization. b. Inhibition of the motor activity of myosin.arrow_forwardWhat is the general role of the gene product of SRY in human sex determination? Also, on which chromosome(s) is the SRY gene normally located?arrow_forward
- As we have focused on sex differentiation, sex chromosomes, and genetic mechanisms involved in sex determination. At the same time, we found manyopportunities to consider the methods and reasoning by whichmuch of this information was acquired. From the explanationsgiven in the chapter, you should answer the following fundamentalquestion: How do we know that X chromosomal inactivation of eitherthe paternal or maternal homolog is a random event duringearly development in mammalian females?arrow_forwardIn Drosophila, the X chromosomes may become attached to one another (XXn ) such that they always segregate together. Some flies thus contain a set of attached X chromosomes plus a Y chromosome. (a) What sex would such a fly be? Explain why this is so. (b) Given the answer to part (a), predict the sex of the off-spring that would occur in a cross between this fly and a normal one of the opposite sex. (c) If the offspring described in part (b) are allowed to interbreed, what will be the outcome?arrow_forwardA male Drosophila melanogaster has the genotype A/a; B/b; C/c; XD/Y (all genes are on separate chromosomes). How many different sperm genotypes can it produce through meiosis of one single pre-gametic (2n) cell? (remember, there is no crossing over in male Drosophila) Explain.arrow_forward
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