17. Mutation, Repair, and Recombination

Types of Mutations

Open Question
Marfan syndrome is an autosomal dominant disorder in humans. It results from mutation of a gene on chromosome 15 that produces the connective tissue protein fibrillin. In its wild-type form, fibrillin gives connective tissues, such as cartilage, elasticity. When mutated, however, fibrillin is rigid and produces a range of phenotypic complications, including excessive growth of the long bones of the leg and arm, sunken chest, dislocation of the lens of the eye, and susceptibility to aortic aneurysm, which can lead to sudden death in some cases.Different sets of symptoms are seen among various family members, as shown in the pedigree below. Each quadrant of the circles and squares represents a different symptom, as the key indicates.All cases of Marfan syndrome are caused by mutation of the fibrillin gene, and all family members with Marfan syndrome carry the same mutant allele. What do the differences shown in the phenotypes of family members say about the expression of the mutant allele?
Open Question
Two different mutations are identified in a haploid strain of yeast. The first prevents the synthesis of adenine by a nonsense mutation of the ade-1 gene. In this mutation, a base-pair substitution changes a tryptophan codon (UGG) to a stop codon (UGA). The second affects one of several duplicate tRNA genes. This base-pair substitution mutation changes the anticodon sequence of a tRNAᵀʳᵖ from

3′−ACC−5′ to 3′−ACU−5′

Assuming there are no other mutations in the genome, will this double-mutant yeast strain be able to grow on minimal medium? If growth will occur, characterize the nature of growth relative to wild type.
Multiple Choice
A mutation occurred that changed the sequence 5' AAGCTTGC 3' to 5' AAGCTTTGC 3'. What is the name for this type of mutation?
Multiple Choice
Which of the following mutations changes one codon to a chemically different amino acid?
Multiple Choice
Which of the following point mutations changes a purine nucleotide to a pyrminidine nucleotide?
Multiple Choice
Changes in the codon reading frame can be caused from all but which of the following?
Open Question
Identify the normal functions of the following genes whose mutations are associated with the development of cancer.

c-MYC(Burkitt lymphoma)
Open Question
Identify the normal functions of the following genes whose mutations are associated with the development of cancer.

APC(familial adenomatous polyposis)
Open Question
Identify the normal functions of the following genes whose mutations are associated with the development of cancer.

Which of these genes would you classify as a proto-oncogene and which as a tumor suppressor gene? Explain your categorization for each gene.
Open Question
Identify the normal functions of the following genes whose mutations are associated with the development of cancer.

p53(Li–Fraumeni syndrome)
Open Question
Identify the normal functions of the following genes whose mutations are associated with the development of cancer.

RB1(retinoblastoma)
Open Question
In this chapter, we focused on how gene mutations arise and how cells repair DNA damage. At the same time, we found opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter,

How do we know that mutations occur randomly?
Open Question
Go online to the Online Mendelian Inheritance of Man (OMIM) website. Look up the following genetic conditions and answer the questions posed about them.

Go to the 'Molecular Genetics' section and describe the most common mutation of the CF gene.
Open Question
Go online to the Online Mendelian Inheritance of Man (OMIM) website. Look up the following genetic conditions and answer the questions posed about them.

Look up cystic fibrosis (CF), OMIM 602421, and give the gene name and abbreviation and the chromosome location of the gene.
Open Question
Go online to the Online Mendelian Inheritance of Man (OMIM) website. Look up the following genetic conditions and answer the questions posed about them.

Go to the 'Population Genetics' section discussing the TSD gene. In a few sentences, summarize the human population in which TSD is most frequently found and give the approximate frequency of heterozygous carriers for the TSD mutation in North American Jews.