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 26ESP
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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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.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?)
. 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.
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
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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- 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_forwardSexual 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_forwardWith relevance to sex determination in humans, discuss: i) X chromosome inactivation; and ii) Testicular feminization Provide detail examples.arrow_forward
- If a genetic female fetus is exposed to testosterone in utero, would that individual develop a complete male phenotypic sex, partial male phenotypic sex, or a normal female phenotypic sex? Explain your answer, describing the sex phenotype of the gonads, internal genital ducts and external genitalia. What would the developmental outcomes be if the fetus were instead exposed to dihydrotestosterone in utero?arrow_forwardIn humans, the AR gene is located on the X chromosome. If a person who is XY has a complete deletion of the AR gene, do you think giving them testosterone injections during puberty would cause an increase in expression of male secondary sex characteristics compared to not receiving injections? Explain your answer.arrow_forwardIn 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).arrow_forward
- Gametogenesis in mammals is a complex process. When comparing spermatogenesis and oogenesis, indicated whether the follow statements are true or false. After the S phase, both the spermatogonial stem cell and primary oocyte have the same number of double-copy chromosomes. #analyze Question 1 options: True False Both the first polar body and the second polar body have the same number of chromosomes. #analyze Question 2 options: True False After the S phase, both the spermatogonial stem cell and primary oocyte have the same number of double-copy chromosomes. #analyze Question 3 options: True False Both the primary oocyte and the secondary spermatocyte have double-copy chromosomes. #analyze Question 4 options: True Falsearrow_forwardWhat will be the effect on sexual development in newly fertilized Drosophila embryos if the following genes are deleted? Q. sex-lethalarrow_forwardSuppose you are analyzing the DNA from the polar bodies formed during human oogenesis. If the woman who produced the oocyte has a mutation in a known disease gene, would analyzing the polar body DNA allow you to infer whether the mutation is present in the mature oocyte? Explain.arrow_forward
- Mutations Can Uncouple chromosomal Sex from Phenotypic Sex Discuss whether the following individuals (1) have male or female gonads, (2) are phenotypically male or female (discuss Wolffian/Mllerian ducts and external genitalia), and (3) are sterile or fertile. a. XY, homozygous for a recessive mutation in the testosterone biosynthetic pathway, producing no testosterone b. XX, heterozygous for a dominant mutation in the testosterone biosynthetic pathway, which causes continuous production of testosterone c. XY, heterozygous for a recessive mutation in the MIH gene d. XY, homozygous fora recessive mutation in the SRY gene that abolishes functionarrow_forwardWhat pathway is Fog2 gene product a part of and how does it affect sex determination?arrow_forwardWhat will be the effect on sexual development in newly fertilized Drosophila embryos if the following genes are deleted? Q. doublesexarrow_forward
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