Concepts of Genetics (11th Edition)
11th Edition
ISBN: 9780321948915
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino
Publisher: PEARSON
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Chapter 7, Problem 1PDQ
HOW DO WE KNOW? In this chapter, we have focused on sex differentiation, sex chromosomes, and genetic mechanisms involved in sex determination. At the same time, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, you should answer the following fundamental questions?
- (a) How do we know whether or not a heteromorphic chromosome such as the Y chromosome plays a crucial role in the determination of sex?
- (b) How do we know that in humans the X chromosomes play no role in human sex determination, while the Y chromosome causes maleness and its absence causes femaleness?
- (c) How do we know that Drosophila utilizes a different sex-determination mechanism than mammals, even though it has the same sex-chromosome compositions in males and females?
- (d) How do we know that X chromosomal inactivation of either the paternal or maternal homolog is a random event during early development in mammalian females?
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How do we know whether or not a heteromorphic chromosome such as the Y chromosome plays a crucial role in the determination of sex?
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.
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.
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Chapter 7 Solutions
Concepts of Genetics (11th Edition)
Ch. 7 - Prob. 1NSTCh. 7 - Campomelic dysplasia (CMD1) is a congenital human...Ch. 7 - Carbon Copy (CC), the first car produced from a...Ch. 7 - Prob. 1CSCh. 7 - Prob. 2CSCh. 7 - Prob. 3CSCh. 7 - Prob. 4CSCh. 7 - HOW DO WE KNOW? In this chapter, we have focused...Ch. 7 - Review the Chapter Concepts list on p. 151. These...Ch. 7 - Prob. 3PDQ
Ch. 7 - Prob. 4PDQCh. 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 - Prob. 23PDQCh. 7 - Prob. 24PDQCh. 7 - Prob. 25PDQCh. 7 - Prob. 26PDQCh. 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 - Prob. 31ESPCh. 7 - In mice, the X-linked dominant mutation Testicular...Ch. 7 - When the cloned cat Carbon Copy (CC) was born (see...Ch. 7 - Prob. 34ESPCh. 7 - In chickens, a key gene involved in sex...Ch. 7 - Prob. 36ESP
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- Human sex chromosomes are XX for females and XY for males. a. With respect to an X-linked gene, how many different types of gametes can a male produce? b. If a female is homozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele? c. If a female is heterozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele?arrow_forwardHuman females have two X chromosomes (XX); males have one X and one Y chromosome (XY). a. With respect to X chromosome alleles, how many different types of gametes can a male produce? b. If a female is homozygous for an allele on an X chromosome, how many types of gametes can she produce with respect to that allele? c. If a female is heterozygous for an X chromosome allele, how many types of gametes can she produce with respect to that allele?arrow_forwardA sperm cell from the fruit fly Drosophila melanogaster contains four chromosomes. How many chromosomes would be present in a spermatogonial cell about to enter meiosis? How many chromatids would be present in a spermatogo- nial cell at metaphase I of meiosis? How many would be present at metaphase II?arrow_forward
- From 80% to 90% of the most common human chromosome abnormalities arise because the chromosomes fail to divide properly in oogenesis. Can you think of a reason why failure of chromosome division might be more common in female gametogenesis than in male gametogenesis?arrow_forwardWhat is the difference between the X-Y and X-0 systems of sex determination?arrow_forward. With regards to the grasshopper testes experiment, diakinesis is an ideal stage to determine chromosome number due to the degree of condensation of the chromosomes? Count the chromosomes at this stage. Does it represent a diploid or a haploid number?arrow_forward
- In oogenesis--> other than allowing for the elimination of one half of the diploid chromosomes, what is the purpose of the polar bodies? do they provide any resources?arrow_forwardThough an individual with abberations such as Robertsonian translocation may be phenotypically normal, they can generate gametes through meiosis that have atypical organizations of chromosomes, resulting in recurrent fetal abnormalities or miscarriages. Why, despite these Robertsonian translocations, are affected cells still able to generate typical gametes through meiosis?arrow_forward. A mature female wolf, with 78 diploid chromosomes in each somatic cell, produces haploid oocytes (egg cells) containing how many chromosomes per cell? 1 sex-determining chromosome (Y) and 38 autosomes 2 sex-determining chromosomes (XX) and 76 autosomes 1 sex-determining chromosome (X) and 39 autosomes 2 sex-determining chromosomes (XY) and 76 autosomes 1 sex-determining chromosome (X) and 38 autosomesarrow_forward
- What is the purpose of meiosis? In other words, why create haploid cells?arrow_forwardA company that offers PGD terms an embryo “normal and healthy” if it has 46 chromosomes. Why is this statement misleading? , Two famous male actors had twins using a surrogate mother who carried two embryos that hadbeen fertilized in vitro, one with one man’s sperm and the other with the other man’s sperm. In terms of genetics, how closely are the babies, a boy and a girl, related to each other if they have different fathers?arrow_forwardWhy does a single X chromosome cause infertility and other abnormalities in Turner Syndrome subjects?arrow_forward
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