Chapter 15: Problem 6
Why is a random mutation more likely to be deleterious than beneficial?
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Chapter 15: Problem 6
Why is a random mutation more likely to be deleterious than beneficial?
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Why would a mutation in a somatic cell of a multicellular organism escape detection?
In maize, a \(D s\) or \(A c\) transposon can cause mutations in genes at or near the site of transposon insertion. It is possible for these elements to transpose away from their original site, causing a reversion of the mutant phenotype. In some cases, however, even more severe phenotypes appear, due to events at or near the mutant allele. What might be happening to the transposon or the nearby gene to create more severe mutations?
A yeast strain that has a regulated overexpression of HindIII endonuclease has been generated. What would be the consequence of this overexpression? Which repair pathway may be functional in this yeast cell and why?
A significant number of mutations in the \(H B B\) gene that cause human \(\beta\) -thalassemia occur within introns or in upstream noncoding sequences. Explain why mutations in these regions often lead to severe disease, although they may not directly alter the coding regions of the gene.
Mutations in the \(I L 2 R G\) gene cause approximately 30 percent of severe combined immunodeficiency disorder (SCID) cases. These mutations result in alterations to a protein component of cytokine receptors that are essential for proper development of the immune system. The \(I L 2 R G\) gene is composed of eight exons and contains upstream and downstream sequences that are necessary for proper transcription and translation. Below are some of the mutations observed. For each, explain its likely influence on the \(I L 2 R G\) gene product (assume its length to be 375 amino acids). (a) Nonsense mutation in coding regions (b) Insertion in Exon 1 , causing frameshift (c) Insertion in Exon \(7,\) causing frameshift (d) Missense mutation (e) Deletion in Exon 2 , causing frameshift (f) Deletion in Exon 2 , in frame (g) Large deletion covering Exons 2 and 3
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