Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 4, Problem 50P
In marsupials like the opposum or kangaroo, X inactivation selectively inactivates the paternal X chromosome.
| a. | Predict the possible coat colors of the progeny of both sexes if a female marsupial homozygous for a mutant allele of an X-linked coat color gene was mated with a male hemizygous for the alternative wild-type alleles of this gene. |
| b. | Predict the possible coat colors of progeny of both sexes if a male marsupial hemizygous for an allele of an X-linked coat color gene was mated with a female homozygous for the alternative wild-type allele of this gene. |
| c. | Why are the terms recessive and dominant not useful in describing the alleles of X-linked coat color genes in marsupials? |
| d. | Why would marsupials heterozygous for two alleles of an X-linked coat color gene not have patches of fur of two different colors as did the tortoiseshell cats described in the previous problem? |
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XX individuals can be sex-reversed males if one of their X chromosomes contains a translocated
portion of the Y chromosome that includes the SRY gene. In light of what you now know about
X-chromosome inactivation, it seems that this karyotype might have more complex
consequences. In fact, although most such males are completely sex-reversed, X-chromosome
inactivation can cause some of these XX males to have varying degrees of residual female
characteristics.
a. X-chromosome inactivation in normal XX embryos occurs earlier in development than
SRY production in normal XY embryos. When present on a translocation X
chromosome, SRY is subject to inactivation. Formulate a hypothesis to explain why
many XX individuals with a translocation X chromosome that includes the SRY gene are
not completely sex-reversed (male).
b. Based on your answer to part (a), why do you think some individuals with this karyotype
are completely sex-reversed?
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…
. 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.
Chapter 4 Solutions
Genetics: From Genes to Genomes
Ch. 4 - Choose the best matching phrase in the right...Ch. 4 - Humans have 46 chromosomes in each somatic cell....Ch. 4 - The figure that follows shows the metaphase...Ch. 4 - Human XX males who are sex-reversed because they...Ch. 4 - Researchers discovered recently that the sole...Ch. 4 - One oak tree cell with 14 chromosomes undergoes...Ch. 4 - Indicate which of the cells numbered iv matches...Ch. 4 - a. What are the four major stages of the cell...Ch. 4 - Answer the questions that follow for each stage of...Ch. 4 - Can you think of anything that would prevent...
Ch. 4 - One oak tree cell with 14 chromosomes undergoes...Ch. 4 - Which types of cell division mitosis, meiosis I,...Ch. 4 - Complete the following statements using as many of...Ch. 4 - The five cells shown in figure a e are all from...Ch. 4 - One of the first microscopic observations of...Ch. 4 - A person is simultaneously heterozygous for two...Ch. 4 - Assuming i that the two chromosomes in every...Ch. 4 - In the moss Polytrichum commune, the haploid...Ch. 4 - Can you think of anything that would prevent...Ch. 4 - Sister chromatids are held together through...Ch. 4 - The pseudoautosomal regions PARs of the X and Y...Ch. 4 - Remarkably, the platypus has 10 sex chromosomes,...Ch. 4 - Somatic cells of chimpanzees contain 48...Ch. 4 - In humans: a. How many sperm develop from 100...Ch. 4 - Women sometimes develop benign tumors called...Ch. 4 - In a certain strain of turkeys, unfertilized eggs...Ch. 4 - Imagine you have two pure-breeding lines of...Ch. 4 - A system of sex determination known as...Ch. 4 - In Drosophila, the autosomal recessive brown eye...Ch. 4 - Barred feather pattern is a Z-linked dominant...Ch. 4 - When Calvin Bridges observed a large number of...Ch. 4 - In a vial of Drosophila, a research student...Ch. 4 - In 1919, Calvin Bridges began studying an X-linked...Ch. 4 - In Drosophila, a cross was made between a...Ch. 4 - As we learned in this chapter, the white mutation...Ch. 4 - The following is a pedigree of a family in which a...Ch. 4 - Each of the four pedigrees that follow represents...Ch. 4 - The pedigree that follows indicates the occurrence...Ch. 4 - Duchenne muscular dystrophy DMD is caused by a...Ch. 4 - The X-linked gene responsible for DMD encodes a...Ch. 4 - Males have hemophilia when they are hemizygous for...Ch. 4 - In the Fast Forward Box Visualizing X Chromosome...Ch. 4 - Consider the following pedigrees from human...Ch. 4 - Several different antigens can be detected in...Ch. 4 - The ancestry of a white female tiger bred in a...Ch. 4 - The pedigree that follows shows the inheritance of...Ch. 4 - In 1995, doctors reported a Chinese family in...Ch. 4 - In cats, the dominant O allele of the X-linked...Ch. 4 - In marsupials like the opposum or kangaroo, X...Ch. 4 - The pedigree diagram below shows a family in which...
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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 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_forwardBarr bodies are formed to adjust X chromosome dosage in species other than humans, such as Drosophila (fruit flies) and C. elegans (nematodes). True or False ?arrow_forwardAn attached-X female fly, XX ¬Y (see the “Insights and Solutions” box), expresses the recessive X-linked white-eye mutation. It is crossed to a male fly that expresses the X-linked recessive miniature-wing mutation. Determine the outcome of this cross in terms of sex, eye color, and wing size of the offspring.arrow_forward
- . In humans, hemophilia is an X-linked recessive gene and will only be expressed in females if they are homozygous for this gene. However, in some rare cases, a heterozygote becomes hemophilic. Explain how this incident happens and why will there be skewed X-inactivation?arrow_forwardThe Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings; Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Give the phenotypes and proportions of progeny produced in the following crosses. Q. A red-eyed Notch female is mated with a white-eyed male.arrow_forwardThe Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings; Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Give the phenotypes and proportions of progeny produced in the following crosses. Q.A white-eyed Notch female is mated with a white-eyed male.arrow_forward
- The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings; Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Give the phenotypes and proportions of progeny produced in the following crosses. a. A red-eyed Notch female is mated with a white-eyed male. b. A white-eyed Notch female is mated with a red-eyed male. c. A white-eyed Notch female is mated with a white-eyed male.arrow_forwardThe Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings; Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Give the phenotypes and proportions of progeny produced in the following crosses. Q.A white-eyed Notch female is mated with a red-eyed male.arrow_forwardAnhidrotic ectodermal dysplasia is an X-linked recessive disorder in humans characterized by small teeth, no sweat glands, and sparse body hair. This trait is usually seen in men, but women who are heterozygous carriers of the trait often have irregular patches of skin with few or no sweat glands (see the illustration below). Q. Explain why women who are heterozygous carriers of a recessive gene for anhidrotic ectodermal dysplasia have irregular patches of skin lacking sweat glands.arrow_forward
- Which of the following statements about calico cats is true? Select all that apply. Black fur sections are found in regions that are formed from cells that inactivated the X chromosome with the orange allele of the fur color gene. a. Black and orange sections of fur on calico cats will always be the same size, since X chromosome inactivation always happens at the same stage of development. b. Black fur sections are found in regions that are formed from cells that inactivated the paternal X chromosome. C. Black sections of fur in calico cats will always be located on the same body locations. d. Calico cats are only females, except in cases of chromosomal number abnormalities. D e.arrow_forwardIn Drosophila, the X-linked recessive mutation vermilion (v) causes bright red eyes, in contrast to the brick-red eyes of wild type. A separate autosomal recessive mutation, suppressor of vermilion (su-v), causes flies homozygous or hemizygous for v to have wildtype eyes. In the absence of vermilion alleles, su-v has no effect on eye color. Determine the F1 and F2 phenotypic ratios from a cross between a female with wild-type alleles at the vermilion locus, but who is homozygous for su-v, with a vermilion male who has wildtype alleles at the su-v locusarrow_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_forward
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