Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 7, Problem 29ESP
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 (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?
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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 (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?
Which of the following is true about sex determination in mammals? Choose all possible answers.
a.) The conversion of the genital ridge into the bipotential gonad requires the Sf1, Wt1, and Lhx9 transcription factors.
b.) Even if one of the transcription factors mentioned in choice a (Sf1, Wt1, and Lhx9) will lose its function, the normal development of either male or female gonads will still push through.
c.) Sry protein binds to the enhancer of the Sox9 gene and elevates expression of this key gene in the ovary-determining pathway.
d.) β-catenin functions to initiate the ovarian pathway of development by activating the genes involved in granulosa cell differentiation.
e.) Sf1 protein prevents the production of Sox9.
The diagram in Figure 1 shows a section through the mammalian testis. With reference to this diagram answer the following questions:
FIGURE 1
(a) What percentage of each of the following types of cells would you expect to contain an X chromosome.
Give a REASON for your answer in each case.
i) type cell A
ii) type cell B
(b)Name the cell type labelled B which under goes mitosis.
State the importance of mitosis in a mature testis.
Chapter 7 Solutions
Concepts of Genetics (12th Edition)
Ch. 7 - Campomelic dysplasia (CMD1) is a congenital human...Ch. 7 - Carbon Copy (CC), the first car produced from a...Ch. 7 - Gender is someones conscious and unconscious...Ch. 7 - Gender is someones conscious and unconscious...Ch. 7 - HOW DO WE KNOW? In this chapter, we have focused...Ch. 7 - Review the Chapter Concepts list on p. 151. These...Ch. 7 - Distinguish between the concepts of sexual...Ch. 7 - Contrast the XX/XY and XX/X0 modes of sex...Ch. 7 - Describe the major difference between sex...Ch. 7 - How do mammals, including humans, solve the dosage...
Ch. 7 - The phenotype of an early-stage human embryo is...Ch. 7 - What specific observations (evidence) support the...Ch. 7 - Describe how nondisjunction in human female...Ch. 7 - An insect species is discovered in which the...Ch. 7 - When cows have twin calves of unlike sex...Ch. 7 - An attached-X female fly, XXY (see the Insights...Ch. 7 - Assume that on rare occasions the attached X...Ch. 7 - It has been suggested that any male-determining...Ch. 7 - What is a Barr body, and where is it found in a...Ch. 7 - Indicate the expected number of Barr bodies in...Ch. 7 - Define the Lyon hypothesis.Ch. 7 - Can the Lyon hypothesis be tested in a human...Ch. 7 - Predict the potential effect of the Lyon...Ch. 7 - Cat breeders are aware that kittens expressing the...Ch. 7 - In mice, the Sry gene (see Section 7.2) is located...Ch. 7 - The genes encoding the red-and...Ch. 7 - What is the role of the enzyme aromatase in sexual...Ch. 7 - In the wasp Bracon hebetor, a form of...Ch. 7 - The Amami spiny rat (Tokudaia osimensis) lacks a Y...Ch. 7 - In mice, the X-linked dominant mutation Testicular...Ch. 7 - When the cloned cat Carbon Copy (CC) was born (see...Ch. 7 - In reptiles, sex determination was thought to be...Ch. 7 - In chickens, a key gene involved in sex...
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