ESSENTIALS OF GENETICS-MODIFIED ACCESS
9th Edition
ISBN: 9780134190006
Author: KLUG
Publisher: PEARSON
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Chapter 5, Problem 27PDQ
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 onlyin 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 15). 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?
The development of sex and gender is a good example of a developmental cascade because:
Group of answer choices
Although having an X and a Y chromosome at conception typically leads to the development of testes during prenatal development, this may not lead to typical male genitalia if certain hormones are present later in development
Two people may have the same gonads early in prenatal development but end up with different external genitalia and gender identities as a result of differences in the prenatal environment
All of the options listed here are correct
Having two X chromosomes at conception typically leads to the development of ovaries during prenatal development, which typically leads to high levels of estrogen in puberty, which typically leads to a female gender identity in adulthood
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.
Chapter 5 Solutions
ESSENTIALS OF GENETICS-MODIFIED ACCESS
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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- Sexual differentiation begins close to 4 weeks after fertilization, but cannot be seen visually until about 6 weeks post fertilization. All fetuses begin with a ______________________ gonad that is able to become either ovaries or testes, depending on the presence or absence of the Y chromosome. If the Y chromosome is present, a region of the Y chromosome will begin expressing genes that start the process of masculinization of internal structures. This region is known as the ______________________________ region or ___________ for short. The expression of these genes causes the bipotential gonad to develop into the testes. Once the testes have started developing, two hormones, testosterone and Anti-MüllerianHormone are produced. Testosterone causes the _____________________ ducts to develop into the _____________________. Testosterone also causes the internal development of the __________________ and __________________. Anti-Müllerian Hormone causes the ______________________ ducts…arrow_forwardIt is estimated that in about 1/150,000 births, an individual is born with 46 chromosomes, both an X and a Y chromosome, but is externally a phenotypic female at birth. A mutation in the gene for which protein is the most likely explanation for this condition? A. Chorionic gonadotropin B. Anti-Müllerian hormone receptor C. Testes determining factor D. Wolffian regression factor (WRF) E. Estrogen receptor βarrow_forwardWhat will be the effect on sexual development in newly fertilized Drosophila embryos if the following genes are deleted? Q. doublesexarrow_forward
- A primary oocyte divides to give rise to a secondary oocyte and a first polar body. The secondary oocyte then divides to give rise to an ovum and a second polar body. Q. Is the genetic information found in the first polar body identical with that found in the secondary oocyte? Explain your answerarrow_forwardWhat will be the effect on sexual development in newly fertilized Drosophila embryos if the following genes are deleted? Q. sex-lethalarrow_forwardDraw a Punnett square. cross an XX woman with an XY man. How many kinds of eggs can a woman produce in terms of their sex chromosomes? How many kinds of sperm cells can men produce in terms of their sex chromosomes? In any given fertilization event, what is the chance that a child will be XX? XY? In any given fertilization event, what is the chance that a child will be male? Female?arrow_forward
- The Amami spiny rat (Tokudaia osimensis) lacks a Y chromosome, yet scientists at Hokkaido University in Japan have reported that key sex-determining genes continue to be expressed in this species. Provide possible explanations for why male differentiation can still occur in this mammalian species despite the absence of a Y chromosome.arrow_forwardThe vast majority of mRNA placed into the developing oocyte do NOT get translated until afterfertilization – how does this happen?arrow_forwardFill in the blank. Maternal effect occurs because proteins and RNA specified by maternal genes accumulate in the _____ of the oocyte and influence the early development of the embryo.arrow_forward
- Which of the following could explain how might a human having the XX sex chromosomes can develop as a male? Both of his X chromosomes become inactivated giving rinse to a male. The autosomal Sox9 gene is inactivated in the male. This is not possible. His father suffered a chromosomal translocation in the reproductive cells that moved the SRY region to the X chromosome. The ratio of X chromosomes to haploid sets of chromosomes has been altered.arrow_forwardIn 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_forward. 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.arrow_forward
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