Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 7, Problem 14PDQ
It has been suggested that any male-determining genes contained on the Y chromosome in humans cannot be located in the limited region that synapses with the X chromosome during meiosis. What might be the outcome if such genes were located in this region?
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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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In Drosophila, the X chromosomes may become attached to one another (XXn ) such that they always segregate together. Some flies thus contain a set of attached X chromosomes plus a Y chromosome. (a) What sex would such a fly be? Explain why this is so. (b) Given the answer to part (a), predict the sex of the off-spring that would occur in a cross between this fly and a normal one of the opposite sex. (c) If the offspring described in part (b) are allowed to interbreed, what will be the outcome?
Though 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?
Chapter 7 Solutions
Concepts of Genetics (12th Edition)
Ch. 7 - Campomelic dysplasia (CMD1) is a congenital human...Ch. 7 - Carbon Copy (CC), the first car produced from a...Ch. 7 - Gender is someones conscious and unconscious...Ch. 7 - Gender is someones conscious and unconscious...Ch. 7 - HOW DO WE KNOW? In this chapter, we have focused...Ch. 7 - Review the Chapter Concepts list on p. 151. These...Ch. 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 - 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 - The Amami spiny rat (Tokudaia osimensis) lacks a Y...Ch. 7 - In mice, the X-linked dominant mutation Testicular...Ch. 7 - When the cloned cat Carbon Copy (CC) was born (see...Ch. 7 - In reptiles, sex determination was thought to be...Ch. 7 - In chickens, a key gene involved in sex...
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- During meiosis in male mammals, sex chromosomes segregate to produce two types of sperm: X‑bearing sperm and Y‑bearing sperm. True or false?arrow_forwardA male Drosophila melanogaster has the genotype A/a; B/b; C/c; XD/Y (all genes are on separate chromosomes). How many different sperm genotypes can it produce through meiosis of one single pre-gametic (2n) cell? (remember, there is no crossing over in male Drosophila) Explain.arrow_forwardWhat possible conclusions can be drawn from the observations that in male Drosophila, no crossing over occurs, and that during meiosis, synaptonemal complexes are not seen in males but are observed in females where crossing over occurs?arrow_forward
- In fruit flies, chromosomal crossing over does not occur in meiosis in males, whereas crossing over does occur in meiosis in females. In fruit flies that are heterozygous at many genes (i.e. many maternal and paternal versions of the genes differ), at what stage would cells no longer be heterozygous for any gene during the process of meiosis? a)After the second meiotic division in males, and after the first meiotic division in females. b)After the second meiotic division in both males and females. c)After the first meiotic division in both males and females. d)After the first meiotic division in males, and after the second meiotic division in females.arrow_forwardWhich sex chromosome (X or Y) carries the gene for eye color in Drosophila?arrow_forwardWhat is the probability that, in an organism with a haploid number of 10, a sperm will be formed that contains all 10 chromosomes whose centromeres were derived from maternal homologs?arrow_forward
- Female flies with white eyes and miniature wings (both X-linkedrecessive traits) were crossed to male flies with red eyes and longwings. On rare occasions, female offspring were produced withwhite eyes. If we assume these females are due to errors in meiosis, what would be the most likely chromosomal composition ofsuch flies? What would be their wing length?arrow_forwardHuman 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_forwardIn mice, the Sry gene is located on the Y chromosome very close to one of the pseudoautosomal regions that pairs with the X chromosome during male meiosis. Given this information, propose a model to explain the generation of unusual males who have two X chromosomes (with an Sry-containing piece of the Y chromosome attached to one X chromosome).arrow_forward
- If nondisjunction occurs in humans for one pair of homologous chromosomes during meiosis I. The other pairs segregate normally. a) Will any normal gametes result? b) How many chromosomes will each human gametehave? If nondisjunction occurs in humans for sister chromatids during meiosis II. The other pairs segregate normally. a) Will any normal gametes result? b) How many chromosomes will each human gamete have?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_forwardDuring metaphase I of meiosis, tetrads align along the metaphase plate independently of each other. Therefore, there is a random “shuffle” of maternal and paternal chromosomes in the resulting gametes.The following diagram demonstrates how this works in a diploid cell with four chromosomes (2n=4) . Because there are two pairs of chromosomes and each pair can align in one of two ways during metaphase I, the number of possible variations in the gametes produced is 22 or 4.For an organism that is , there are three pairs of chromosomes, so the number of possible variations in the gametes produced due to independent assortment in metaphase I is 23 or 8. In an organism with a haploid number of 7, how many possible combinations of maternal and paternal chromosomes can occur in its gametes? a. 72=49 b. 27=128 c.17=1 d. 214=16 384arrow_forward
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