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 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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A diploid organism produces four gametes from one parent cell through the process of meiosis. Two gametes are found to have 7 chromosomes and two gametes are found to have 5 chromosomes.
A) Is this the expected number of chromosomes that would be found in each gamete following a normal cycle of meiosis? If yes, explain why. If no, explain why not and describe how the gamete situation described above occurred.
B) Determine the number of homologous chromosome pairs that the original parent cell contained, before meiosis began. Explain how you determined this value.
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.
Question is also in the picture.
A) Give the diploid number of this organism.
B) Is it mitosis or meiosis? Give two (2) elements on which you base your reasoning.
C) Identify this mystery phase of the cell cycle.
D) How many daughter cells will be produced at the end of the process and how many chromosomes (in numbers) will they contain?
E) How does this process ensure the genetic variability of individuals of the species? Your answer must be based on two (2) different elements.
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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- 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?arrow_forwardWhat are the non-random events that occur during sexual reproduction (post-meiosis) in humans? Please be specific on naming the events.arrow_forwardThe mouse haploid genome contains about 2.9 × 109 nucleotide pairs of DNA. Indicate how many nucleotide pairs of DNA are present in each of the following mouse cells: (a) somatic cell, (b) sperm cell, (c) fertilized egg,(d) primary oocyte, (e) first polar body, (f) secondary spermatocyte.arrow_forward
- I am a little confused on this question.arrow_forwardIf the amount (mass) of DNA in a diploid cell during G1 phase prior to meiosis I is 8 pg (picograms), how much DNA would be present in a daughter cell immediately following: A) meiosis I? B) meiosis II? (for your information, this cell will function as a gamete) HINT: Go through the process of meiosis one step at a time. DNA replication would double the amount of DNA in the cell, cell division divides the DNA into two daughter cells.arrow_forwardWhich of these questions is not scientifically testable and why?arrow_forward
- You are investigating two temperature-sensitive mutant cells. In one, you can inactivate shugoshin activity by raising the temperature slightly at the start of meiosis. In the other, you can similarly inactivate separase activity by raising the temperature. How would the two cells be affected by inactivating these proteins?arrow_forwardOne reason that worker bees forgo their own reproduction to help their sister (the queen) reproduce is that female bees are more closely related to their sisters than they are to their own offspring. This quirk of genetics results from the fact that bees have haplodiploid sex determination, in which females are diploid, with a mother and a father, but males are haploid, developing from unfertilized eggs. Because males are haploid, they produce sperm by mitosis. Explainwhy haplodiploid sex determination causes females to be more closely related to their sisters than to their offspring.arrow_forwardFor part c, do they consider the total sex chromosomes to be 2 or 3?arrow_forward
- You are an allele on a single uncondensed chromosome in a Yellowfever-carrying mosquito (Aedes aegypti) diploid cell (2n = 6). Demonstrate in as much detail as possible (1) how you will get to each genetically identical diploid cell of the multicellular offspring; (2) how you will get to the next generation of sexually reproduced progeny. Help, I no understand. Perhaps you will?arrow_forward4. a) Female swamp wallabies have 5 pairs of homologous chromosomes. Based on this al one, how many genetically different gametes can be produced by this animal? b) is through independent assortment. At what stage of meiosis One way that genetic diversity of gametes is produced does this occur? c) meiosis which further increases the genetic diversity of gametes. Describe both the process and at what stage of meiosis it occurs. Explain an additional process that occurs duringarrow_forwardThe diagram below shows a cell during Meiosis II: a) What phase of Meiosis II is the cell in? How do you know? b) Assuming all of the chromosomes present during Meiosis II are shown in the figure above, how many chromosomes (counting homologous pairs as two chromosomes) does a gamete from this organism have? c) Draw the same cell during the same phase of Meiosis I. Label the elementsarrow_forward
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