GENETIC ANALYSIS: INTEGRATED - ACCESS
GENETIC ANALYSIS: INTEGRATED - ACCESS
3rd Edition
ISBN: 9780135349298
Author: Sanders
Publisher: PEARSON
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Chapter 11, Problem 39P

Thinking back to the discussion of gain - of - function and loss - of - function mutation in Section 4 .1 , and putting those concepts together with the discussion of base substitution mutation in this chapter, explain why gain - of - function mutation are often dominant and why a loss - of - function mutation are often recessive. Give an example of a type of gain - of - function mutation that is dominant and of a loss - of - function mutation that is recessive.

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Recall that Leber congenital amaurosis (LCA), a formof congenital blindness in humans, can be caused byhomozygosity for recessive mutations in the RPE65gene. Recently, a rare dominant mutation in RPE65has been implicated as one cause of an eye diseasecalled retinitis pigmentosa, which is characterized byretinal degeneration that can progress to blindness.The dominant RPE65 mutation is a missense mutation causing amino acid 447 in the polypeptide tochange from Asp to Glu. Little is known about thenature of the mutant protein.a. Do you think that the dominant allele is morelikely a loss-of-function or a gain-of-functionmutation? Explain.b. As described in this chapter, gene therapy for LCAhas been at least partially successful. Do you thinkthat the same kind of gene therapy can be used forpatients with retinitis pigmentosa caused by thedominant mutant allele of RPE65? Explain.
Leber Congenital Amaurosis (LCA) causes progressive vision loss due to defects in the gene that encodes RPE65 isomerase.  Affected individuals are homozygous recessive for mutant alleles of the RPE65 gene.  You are trying to determine the molecular nature of the mutations in three individuals with LCA.  For ease of analysis, you may assume that each individual is homozygous for the same mutant allele (though the three individuals have different mutations than each other).   You use the polymerase chain reaction to amplify DNA from each patient and you determine the sequence of the DNA and compare it to unaffected individuals.  You identify the following differences.  Note that the non-template strand of DNA is given and the changes are highlighted using red boldface.  You can assume that the sequences are in the first reading frame (eg. the first three nucleotides of each sequence is a codon).   The coding region of the gene is 1602 bp and the position of the sequences shown below is…
Leber congenital amaurosis (LCA) is a form of congenital blindness in humans and is known to be caused by homozygosity for recessive mutations in the RPE65 gene. Recently, a rare dominant mutation in RPE65 has been implicated as one cause of an eye disease called retinitis pigmentosa, which is characterized by retinal degeneration that can progress to blindness. The dominant RPE65 mutation is a missense mutation causing amino acid 447 in the polypeptide to change from Asp to Glu. Little is known about the nature of the mutant protein.  a. Do you think that the dominant allele is more likely a loss-of-function or a gain-of-function mutation? Explain.  b. Recently a group of clinicians and scientists reported that gene therapy (gene replacement therapy) for LCA has been at least partially successful. Do you think that the same kind of gene therapy can be used for patients with retinitis pigmentosa caused by the dominant mutant allele of RPE65? Explain.

Chapter 11 Solutions

GENETIC ANALYSIS: INTEGRATED - ACCESS

Ch. 11 - 11.11 Two different mutations are identified in a...Ch. 11 - What is the phenotype effect of inserting a Ds...Ch. 11 - 11.13 Answer the following questions concerning...Ch. 11 - Several types of mutation are identified and...Ch. 11 - 11.15 A sample of the bacterium is exposed to...Ch. 11 - 11.16 A strain of is identified as having a null...Ch. 11 - Describe the difference between DNA transposons...Ch. 11 - 11.18 How are flanking direct repeat sequences...Ch. 11 - 11.19 Using the adeninethymine base pair in this...Ch. 11 - The partial amino acid sequence of a wild-type...Ch. 11 - Prob. 21PCh. 11 - 11.22 Many human genes are known to have homologs...Ch. 11 - The fluctuation test performed by Luria and...Ch. 11 - In this chapter, three features of genes or of DNA...Ch. 11 - Briefly compare the production of DNA double -...Ch. 11 - During mismatch repair, why is it necessary to...Ch. 11 - 11.27 Following the spill of a mixture of...Ch. 11 - 11.28 In an Ames test using Salmonella bacteria a...Ch. 11 - A wild - type culture of haploid yeast is exposed...Ch. 11 - A fragment of a wild - type polypeptide is...Ch. 11 - Prob. 31PCh. 11 - Alkaptonuria is a human autosomal recessive...Ch. 11 - 11.33 In an experiment employing the methods of...Ch. 11 - Using your knowledge of DNA repair pathways choose...Ch. 11 - 11.35 Ataxia telangiectasia is a human inherited...Ch. 11 - A geneticist searching for mutations uses the...Ch. 11 - 11.37 In a mousebreeding experiment a new mutation...Ch. 11 - 11.38 Considering the Dumbo mutation in a Problem,...Ch. 11 - 11.39 Thinking back to the discussion of...Ch. 11 - 11.40 Common baker’s yeast () is normally grown at...Ch. 11 - 11.41 The two gels illustrated below contain...
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