Essentials of Genetics (9th Edition) - Standalone book
9th Edition
ISBN: 9780134047799
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino
Publisher: PEARSON
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Chapter 5, Problem 19PDQ
Can the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene? Why, or why not?
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Can the Lyon hypothesis be tested in a human female who is homozygousfor one allele of the X-linked G6PD gene? Why, or why not?
Males of many diploid species (like us) have X and Y sex chromosomes. They are hemizygous for most X-
linked genes. Thus, males express most X-linked alleles, whether they are dominant or recessive in
females. In the fruit fly Drosophila, it is common to achieve the equivalent of a test cross of X-linked
genes in females by assessing the readily observed phenotypes of their male progeny. Since males do
not receive X-linked genes from their father, sires of these crosses can be normal or wild-type flies. In fly
genetics, it is conventional to name a gene after the mutant phenotype that enabled its discovery.
Your challenge is to establish gene order and map distances between three X-linked genes in Drosophila.
Each gene is represented by recessive mutant alleles that express rather distinctive phenotypes relative
to their dominant wild-type alternative alleles. Flies expressing fruitless (f) are bisexual, lush (1) have a
heightened responses to ethanol, and ken&barbie (kb) lack external…
Predict the potential effect of the Lyon hypothesis on the retina of a human female heterozygous for the X-linked red-green color blindness trait.
Chapter 5 Solutions
Essentials of Genetics (9th Edition) - Standalone book
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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- Which findings support 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 transgenic mouse with two X-chromosomes and the SRY gene from the Y-chromosome develops male sex organs. A human with an XXXY genotype (Klinefelter syndrome) is phenotypically male. A human with an XO genotype (Turner syndrome) is phenotypically female. a and b, but not c a, b, and carrow_forwardCat breeders are aware that kittens expressing the X-linked calico coat pattern and tortoiseshell pattern are almost invariably females. Why are they certain of this?arrow_forwardExplain why X-linked recessive traits in humans are observed in more males than females.arrow_forward
- The introduction to this chapter described the search for genes that determine pattern baldness in humans. In 1916, Dorothy Osborn suggested that pattern baldness is a sex-influenced trait that is dominant in males and recessive in females. More research suggested that pattern baldness is an X-linked recessive trait. Would you expect to see independent assortment between genetic markers on the X chromosome and pattern baldness if (a) pattern baldness is sexinfluenced and (b) if pattern baldness is X-linked recessive? Explain your answer.arrow_forwardButterflies 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. Question is also in the picture.arrow_forwardIn marsupials like the opposum or kangaroo, X inactivation selectively inactivates the paternal X chromosome.a. Predict the possible coat colors of the progeny ofboth sexes if a female marsupial homozygous for amutant allele of an X-linked coat color gene wasmated with a male hemizygous for the alternativewild-type alleles of this gene.b. Predict the possible coat colors of progeny of bothsexes if a male marsupial hemizygous for an alleleof an X-linked coat color gene was mated with afemale homozygous for the alternative wild-typeallele of this gene.c. Why are the terms recessive and dominant not useful in describing the alleles of X-linked coat colorgenes in marsupials?d. Why would marsupials heterozygous for twoalleles of an X-linked coat color gene not havepatches of fur of two different colors as did the tortoiseshell cats described in the previous problem?51. The pedigree diagram below shows a family in whicharrow_forward
- Let’s suppose that two different X-linked genes exist in mice,designated with the letters N and L. Gene N exists in a dominant,normal allele and in a recessive allele, n, that is lethal. Similarly,gene L exists in a dominant, normal allele and in a recessive allele,l, that is lethal. Heterozygous females are normal, but males thatcarry either recessive allele are born dead. Explain whether or notit would be possible to map the distance between these two genesby making crosses and analyzing the number of living and deadoffspring. You may assume that you have strains of mice in whichfemales are heterozygous for one or both genes.arrow_forwardHuman females have two X chromosomes XX; males have one X and one Y chromosome XY. a. With respect to X-linked alleles, how many different types of gametes can a male produce? b. A female homozygous for an X-linked allele can produce how many types of gametes with respect to that allele? c. A female heterozygous for an X-linked allele can produce how many types of gametes with respect to that allele?arrow_forwardDiscuss the genetic determination of sex and the inheritance of X-linked genes in mammals.arrow_forward
- Analysis of X-Linked Dominant and Recessive Traits In the eighteenth century, a young boy with a skin condition known as ichthyosis hystrix gravior was identified. The phenotype of this disorder includes thickening of skin and the formation of loose spines that are sloughed off periodically. This man married and had six sons, all of whom had the same condition. He also had several daughters, all of whom were unaffected. In all succeeding generations, the condition was passed on from father to son. What can you theorize about the location of the gene that causes ichthyosis hystrix gravior?arrow_forwardNormal vision (XA) in humans is dominant to color blindness (Xa) and is X-linked. A man with normal vision, whose father was colorblind, marries a colorblind woman. What are the chances that a son will be colorblind? What are the chances that a daughter will be colorblind? The determiner for brown eyes (B) is dominant to blue eyes (b) and is not X-linked. A colorblind man with brown eyes, whose mother was blue-eyed, marries a blue-eyed woman having normal vision, whose father was colorblind. Show the expected phenotypes ratio of their children involving eye color, color blindness, and sex.arrow_forwardHuman females who are heterozygous for an X-linked recessive allele sometimes exhibit mild expression of the trait. However, such mild expression of X-linked traits in females who are heterozygous for Xlinked alleles is not seen in Drosophila. What might cause this difference in the expression of X-linked genes between human females and female Drosophila? (Hint: In Drosophila, dosage compensation is accomplished by doubling the activity of genes on the X chromosome of males.)arrow_forward
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