Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN: 9781305251052
Author: Michael Cummings
Publisher: Cengage Learning
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Chapter 7, Problem 12QP
Mutations Can Uncouple chromosomal Sex from
Discuss whether the following individuals (1) have male or female gonads, (2) are phenotypically male or female (discuss Wolffian/Müllerian 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 function
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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.
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?)
In drosophila, a recessive mutation (m-) of a maternal effect gene results in an abnormal phenotype wherein homozygous (m-m-) females produce eggs that cannot support embryonic development. Homozygous (m-m-) males, however, can still produce viable sperm.
(A) Using m+ to denote a normal gene, determine the genotypes and phenotypes of the F1s produce by a cross between a heterozygous female and a recessive male.
(B) From the offspring, backcross the recessive female with the paternal strain. What are the genotypes and phenotypes of the F2s?
(C) If m-m- females produce useless eggs, then how are m-m- produced?
Chapter 7 Solutions
Human Heredity: Principles and Issues (MindTap Course List)
Ch. 7.6 - Prob. 1EGCh. 7.6 - Prob. 2EGCh. 7 - As outlined in this chapter, sex can be defined at...Ch. 7 - As outlined in this chapter, sex can be defined at...Ch. 7 - Prob. 1QPCh. 7 - The Human Reproductive System Discuss and compare...Ch. 7 - Prob. 3QPCh. 7 - A Survey of Human Development from Fertilization...Ch. 7 - Prob. 5QPCh. 7 - Prob. 6QP
Ch. 7 - Prob. 7QPCh. 7 - How Is Sex Determined? The absence of a Y...Ch. 7 - Prob. 9QPCh. 7 - Mutations Can Uncouple Chromosomal Sex from...Ch. 7 - Prob. 11QPCh. 7 - Mutations Can Uncouple chromosomal Sex from...Ch. 7 - Prob. 13QPCh. 7 - Sex-Influenced and Sex-Limited Traits What method...Ch. 7 - Prob. 15QPCh. 7 - Prob. 16QPCh. 7 - Equalizing the Expression of X Chromosome Genes in...Ch. 7 - Equalizing the Expression of X Chromosome Genes in...Ch. 7 - Equalizing the Expression of X Chromosome Genes in...
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- In drosophila, a recessive mutation (m-) of a maternal effect gene results in an abnormal phenotype wherein homozygous (m-m-) females produce eggs that cannot support embryonic development. Homozygous (m-m-) males, however, can still produce viable sperm. Using m+ to denote a normal gene, determine the genotypes and phenotypes of the F1s produce by a cross between a heterozygous female and a recessive male. From the offspring, backcross the recessive female with the paternal strain. What are the genotypes and phenotypes of the F2s? Show COMPLETE cross for both cases. If m-m- females produce useless eggs, then how are m-m- produced?arrow_forwardIn drosophila, a recessive mutation (m-) of a maternal effect gene results in an abnormalphenotype wherein homozygous (m-m-) females produce eggs that cannot support embryonicdevelopment. Homozygous (m-m-) males, however, can still produce viable sperm. Using m+ todenote a normal gene, determine the genotypes and phenotypes of the F1s produce by a crossbetween a heterozygous female and a recessive male. From the offspring, backcross the recessivefemale with the paternal strain. What are the genotypes and phenotypes of the F2s?arrow_forwardThe maternal-effect mutation bicoid (bcd) is recessive. Inthe absence of the bicoid protein product, embryogenesis isnot completed. Consider a cross between a female heterozygousfor the bicoid mutation (bcd+/ bcd-) and a homozygousmale(bcd-/ bcd-). How is it possible for a male homozygous for the mutationto exist?arrow_forward
- EXTRANUCLEAR INHERITANCE In drosophila, a recessive mutation (m-) of a maternal effect gene (MEG) results in an abnormal phenotype wherein homozygous (m-m-) females produce eggs that cannot support embryonic development. Homozygous (m-m-) males, however, can still produce viable sperm. Using m+ to denote a normal gene, determine the genotypes and phenotypes of the F1s produced by a cross between a heterozygous female and a recessive male. From the offspring, backcross the recessive female with the paternal strain. What are the genotypes and phenotypes of the F2s? with COMPLETE cross for both cases.arrow_forwardTOPIC: Sex-linked inheritance Glucose-6-phosphate dehydrogenase deficiency/G6PDD (g) is an X-linked recessive condition wherein the red blood cells of affected individuals undergo premature hemolysis. Fragile X syndrome (F), on the other hand, is an X-linked dominant mutation characterized by a mild to moderate intellectual disability. Amelogenesis imperfecta (AMELY) (A) is a sex-linked congenital disorder affecting the formation of the teeth enamel making affected individuals at higher risk for dental cavities and related problems. Only male offspring inherit this condition. Jane is heterozygous for both X-linked traits like her mother. Her father is normal for both X-linked traits. James has a mother who suffers from G6PDD but not from fragile X-syndrome. His father does not exhibit any X-linked disorder but has amelogenesis imperfecta. What are the genotypes of the following: Jane: ________ James: _________ Jane’s mother: __________…arrow_forwardCampomelic dysplasia (CMD1) is a congenital humansyndrome featuring malformation of bone and cartilage.It is caused by an autosomal dominant mutation of agene located on chromosome 17. Consider the followingobservations in sequence, and in each case, draw whateverappropriate conclusions are warranted.(a) Of those with the syndrome who are karyotypically46,XY, approximately 75 percent are sex reversed,exhibiting a wide range of female characteristics.(b) The nonmutant form of the gene, called SOX9, isexpressed in the developing gonad of the XY male,but not the XX female.(c) The SOX9 gene shares 71 percent amino acid codingsequence homology with the Y-linked SRY gene.(d) CMD1 patients who exhibit a 46,XX karyotypedevelop as females, with no gonadal abnormalities.arrow_forward
- Hemophilia A is caused by a sex-linked recessive gene in human and in dogs. a. What proportions (and sexes), among their offspring will be hemophiliacs if a hemophilic male is mated to a homozygous nonhemophilic female?b. If a daughter produced by the mating in (a) is mated to a normal male, what proportions and (sexes) will be hemophilic among their offspring?arrow_forwardThe 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_forwardPhenylketonuria (PKU) is a disease that results from a recessive gene. Suppose that two unaffected parents produce a child with PKU. a. What is the probability that a sperm from the father will contain the PKU allele? b. What is the probability that an egg from the mother will contain the PKU allele? c. What is the probability that their next child will have PKU? d. What is the probability that their next child will be heterozygous for the PKU gene?arrow_forward
- Glucose-6-phosphate dehydrogenase deficiency/G6PDD (g) is an X-linked recessive conditionwherein the red blood cells of affected individuals undergo premature hemolysis. Fragile X syndrome(F), on the other hand, is an X-linked dominant mutation characterized by a mild to moderateintellectual disability. Amelogenesis imperfecta (A) is a congenital disorder affecting the formation ofthe teeth enamel making affected individuals at higher risk for dental cavities and related problems.Only male offspring inherit this condition. Jane is heterozygous for both X-linked traits like her mother. Her father is normal for both X-linked traits. James has a mother who suffers from G6PDD but not from fragile X-syndrome. His fatherdoes not exhibit any X-linked disorder but has amelogenesis imperfecta. A. What are the genotypes of the following: Jane: ______________________ James: ______________________Jane’s mother: _________________ James’ mother: ________________Jane’s father: __________________…arrow_forwardWhich of the following findings supports the fact that the presence of the Y-chromosome rather than the lack of a second X-chromosome determines the development of maleness in mammals? a. A human with an X0 genotype (Turner syndrome) is phenotypically female. b. A human with an XXY genotype (Klinefelter syndrome) is phenotypically male. c. A transgenic mouse with two X-chromosomes and the SRY gene from the Y-chromosome develops male sex organs. d. b and c, but not a e. a, b, and carrow_forwardBriefly explain the differences between somatic and germ line mutations. Also, tell us what kind of differences you expect to see between autosomal and X-linked mutations which lead to genetic disordersarrow_forward
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