Essentials of Genetics - Masteringgenetic
9th Edition
ISBN: 9780134143699
Author: KLUG
Publisher: PEARSON
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Chapter 5, 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 that in humans the X chromosomes play no role in sex determination, while the Y chromosome causes maleness and its absence causes femaleness?
(b) How did we originally (in the late 1940s) analyze the sex ratio at conception in humans, and how has our approach to studying this issue changed in 2015?
(c) 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?
(d) 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?
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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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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.
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?
Chapter 5 Solutions
Essentials of Genetics - Masteringgenetic
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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- 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_forwardHow do we know whether or not a heteromorphic chromosome such as the Y chromosome plays a crucial role in the determination of sex?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_forward
- A 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_forwardGametogenesis 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_forwardIn 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_forward
- why must sexually reproducing organisms use both processes of mitosis and meiosis, while asexually reproducing organisms only use mitosis?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_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
- What is the purpose of meiosis? In other words, why create haploid cells?arrow_forwardWhy does a single X chromosome cause infertility and other abnormalities in Turner Syndrome subjects?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
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