EBK CONCEPTS OF GENETICS
12th Edition
ISBN: 9780134818979
Author: Killian
Publisher: YUZU
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Chapter 8, Problem 1PDQ
HOW DO WE KNOW? In this chapter, we have focused on chromosomal mutations resulting from a change in number or arrangement of chromosomes. In our discussions, 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, what answers would you propose to the following fundamental questions?
- (a) How do we know that the extra chromosome causing Down syndrome is usually maternal in origin?
- (b) How do we know that human aneuploidy for each of the 22 autosomes occurs at conception, even though most often human aneuploids do not survive embryonic or fetal development and thus are never observed at birth?
- (c) How do we know that specific mutant
phenotypes are due to changes in chromosome number or structure? - (d) How do we know that the mutant Bar-eye phenotype in Drosophila is due to a duplicated gene region rather than to a change in the
nucleotide sequence of a gene?
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The wild-type (normal) fruit fly, Drosophila melanogaster, has straight wings and long bristles. Mutant strains have been isolated with either curled wings or short bristles. The genes representing these two mutant traits are located on separate chromosomes. Carefully examine the data from the five crosses below. (a) For each mutation, determine whether it is dominant or recessive. In each case, identify which crosses support your answer; and (b) define gene symbols and determine the genotypes of the parents for each cross.
The wild-type (normal) fruit fly, Drosophila melanogaster, has straight wings and long
bristles. Mutant strains have been isolated with either curled wings or short bristles.
The genes representing these two mutant traits are located on separate
chromosomes. Carefully examine the data from the five crosses below. (a) For each
mutation, determine whether it is dominant or recessive. In each case, identify
which crosses support your answer; and (b) define gene symbols and determine the
genotypes of the parents for each cross.
Cross
1. straight, short X
straight, short
2. straight, long X
straight, long
3. curled, long X
straight, short
4. straight, short X
straight, short
5. curled, short X
straight, short
straight
wings,
long
bristles
30
120
40
40
20
Number of Progeny
straight
curled
wings, wings,
short
long
bristles
bristles
90
10
0
40
120
60
40
40
0
20
curled
wings,
short
bristles
30
0
40
0
60
Campomelic dysplasia (CMD1) is a congenital humansyndrome featuring malformation of bone and cartilage.It is caused by an autosomal dominant mutation of agene located on chromosome 17. Consider the followingobservations in sequence, and in each case, draw whateverappropriate conclusions are warranted.(a) Of those with the syndrome who are karyotypically46,XY, approximately 75 percent are sex reversed,exhibiting a wide range of female characteristics.(b) The nonmutant form of the gene, called SOX9, isexpressed in the developing gonad of the XY male,but not the XX female.(c) The SOX9 gene shares 71 percent amino acid codingsequence homology with the Y-linked SRY gene.(d) CMD1 patients who exhibit a 46,XX karyotypedevelop as females, with no gonadal abnormalities.
Chapter 8 Solutions
EBK CONCEPTS OF GENETICS
Ch. 8 - A human female with Turner syndrome (47, X) also...Ch. 8 - When two plants belonging to the same genus but...Ch. 8 - What is the effect of a rare double crossover (a)...Ch. 8 - Controlling the overgrowth of invasive aquatic...Ch. 8 - Controlling the overgrowth of invasive aquatic...Ch. 8 - Controlling the overgrowth of invasive aquatic...Ch. 8 - HOW DO WE KNOW? In this chapter, we have focused...Ch. 8 - Review the Chapter Concepts list on page 171....Ch. 8 - Define these pairs of terms, and distinguish...Ch. 8 - For a species with a diploid number of 18,...
Ch. 8 - What evidence suggests that Down syndrome is more...Ch. 8 - What evidence indicates that humans with aneuploid...Ch. 8 - Contrast the fertility of an allotetraploid with...Ch. 8 - Describe the origin of cultivated American cotton.Ch. 8 - Predict how the synaptic configurations of...Ch. 8 - Inversions are said to suppress crossing over. Is...Ch. 8 - Contrast the genetic composition of gametes...Ch. 8 - Human adult hemoglobin is a tetramer containing...Ch. 8 - Discuss Ohnos hypothesis on the role of gene...Ch. 8 - What roles have inversions and translocations...Ch. 8 - The primrose, Primula kewensis, has 36 chromosomes...Ch. 8 - Certain varieties of chrysanthemums contain 18,...Ch. 8 - Drosophila may be monosomic for chromosome 4, yet...Ch. 8 - Mendelian ratios are modified in crosses involving...Ch. 8 - Having correctly established the F2 ratio in...Ch. 8 - The mutations called bobbed in Drosophila result...Ch. 8 - The outcome of a single crossover between...Ch. 8 - A couple planning their family are aware that...Ch. 8 - In a cross in Drosophila, a female heterozygous...Ch. 8 - A woman who sought genetic counseling is found to...Ch. 8 - Prob. 25ESPCh. 8 - In a recent cytogenetic study on 1021 cases of...Ch. 8 - A boy with Klinefelter syndrome (47,XXY) is born...Ch. 8 - Prob. 28ESPCh. 8 - A 3-year-old child exhibited some early indication...Ch. 8 - A normal female is discovered with 45 chromosomes,...
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- If you wanted to make a mouse model for any of the following human genetic conditions (a–d), indicate which of thefollowing types of mice (i–vi) would be useful to your studies. If more than one answer applies, state which type ofmouse would most successfully mimic the human disease:(i) transgenic mouse overexpressing a normal mouse protein; (ii) transgenic mouse expressing normal amounts of amutant human protein; (iii) transgenic mouse expressing adominant negative form of a protein; (iv) a knockout mouse;(v) a conditional knockout mouse; and (vi) a knockin mousein which the normal allele is replaced with a mutant allelethat is at least partially functional. In all cases, the transgeneor the gene that is knocked out or knocked in is a form of thegene responsible for the disease in question.a. Marfan syndrome (a dominant disease caused byhaploinsufficiency for the FBN1 gene);b. A dominantly inherited autoinflammatory diseasecaused by a hypermorphic missense mutation in thegene PLCG2;c.…arrow_forwardThe wild-type (normal) fruit fly, Drosophila melanogaster, has straight wings and long bristles. Mutant strains have been isolated that have either curled wings or short bristles. The genes representing these two mutant traits are located on separate chromosomes. Carefully examine the data from the following five crosses shown below (running across both columns). (a) Identify each mutation as either dominant or recessive. In each case, indicate which crosses support your answer. (b) Assign gene symbols and, for each cross, determine the genotypes of the parents.arrow_forwardWhen a female melanotic fly is crossed with a normal male, the progeny are produced: 123 normal females, 125 melanotic females, and 124 normal males. In subsequent crosses between melanotic females and normal males, melanotic females are frequently obtained, but never any melanotic males. Provide a possible explanation for the inhertiacne of the melanotic mutation (Hint: The cross produces twice as many female progeny as male progeny)arrow_forward
- An individual has a deletion of part of the short arm of chromosome 5. This individual also has a normal copy of chromosome 5. Would you expect this individual to have Cri-du-chat syndrome? Why or why not? Question 7 options: A) Yes, because they will inactivate their normal chromosome 5 B) Yes, because they only contain one copy of some of their genes C) No, because this is a terminal deficiency D) No, because they still have at least one copy of all the genes on chromosome 5arrow_forwardOne of the most famous cases of an X-linked recessive mutation in humans is that of hemophilia found in the descendants of Britain’s Queen Victoria. The pedigree of the royal family indicates that Victoria was heterozygous for the trait; however, her father was not affected, and no other member of her maternal line appeared to carry the mutation. What are some possible explanations of how the mutation arose? What types of mutations could lead to the disease?arrow_forwardIn drosophila, a recessive mutation (m-) of a maternal effect gene results in an abnormal phenotype wherein homozygous (m-m-) females produce eggs that cannot support embryonic development. Homozygous (m-m-) males, however, can still produce viable sperm. (A) Using m+ to denote a normal gene, determine the genotypes and phenotypes of the F1s produce by a cross between a heterozygous female and a recessive male. (B) From the offspring, backcross the recessive female with the paternal strain. What are the genotypes and phenotypes of the F2s? (C) If m-m- females produce useless eggs, then how are m-m- produced?arrow_forward
- The woman in Problem 24 has had two miscarriages. She has come to you, an established genetic counselor, with these questions: Is there a genetic explanation of her frequent miscarriages? Should she abandon her attempts to have a child of her own? If not, what is the chance that she could have a normal child? Provide an informed response to her concerns.arrow_forwardBelow is a pedigree from one family (two parents and eight children). Four of the children (indicated by shaded shapes) are affected with a serious disease with an unknown genetic cause. a) For the disease, what pattern of inheritance (autosomal/sex-linked, recessive/dominant) is exhibited by this pedigree? b) Linkage analysis of the disease to a series of VNTR polymorphisms on human chromosome 5 is shown above. Is there evidence for linkage between the disorder and the VNTR? Briefly explain your answer.arrow_forwardShown below is a pedigree for Phenylketonuria (PKU), an autosomal recessive metabolic disorder. The characteristic feature of PKU is severe mental retardation A) What is the probability that individual II-1 is heterozygous for this gene? B) What is the probability that individual III-4 is heterozygous for this gene? C) If individuals III-3 and III-4 were to marry, what is the probability that their child would express PKU?arrow_forward
- With detailed accounts of their various forms, explain any three of the following chromosomal aberrations: a) Deletions b) Duplications c) Translocations d)Inversionarrow_forwardNow assume that the pedigree shown in question 1 shows the inheritance of a rare genetic disease. a) The disease is most likely autosomal dominant b) The disease is most likely autosomal recessive c) The disease is equally likely to be either autosomal dominant or autosomal recessive, but cannot be x-linked d) Cannot be determined from the information givenarrow_forwardAnswer the following questions: A) Why the extension cannot be 3´---5´ and why it has to be 5´------3´? B) What is a gene?arrow_forward
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