BIO 2110-Genetics Homework 3, due 25 September 2018 3. Shown below are diagrams
ID: 149207 • Letter: B
Question
BIO 2110-Genetics Homework 3, due 25 September 2018 3. Shown below are diagrams for the wild-type (a) and two mutant alleles (b & c) of the Name smrdljiv gene of Mydaus marchei. This gene, which is transcribed in brain and stink gland, is alternatively spliced in these tissues. In the brain, exons 1, 2A & 3 are included in mRNAs. In the stink glands, exons 1, 2B & 3 are included in mRNAs. For each of these alleles, would transcripts be present or not in brain and stink gland? Why or why not. b. TO T 2B 3 C. TAG 2B 3Explanation / Answer
3) In order to transcript present in the brain & stink gland initiation codon require to be present at exon 1 & stop codon require to be placed at exon 3.
In case a (wild type), ATG which is a start codon present in DNA at exon 1. So, it will start transcribe in both brain & stink gland. TGA codon is present in exon 3 which is a stop codon. But the required mRNA transcript can be already transcribe in both brain & stink gland as it is present in the exon 3. So, in case of wild type allele mRNA transcript will be present in both brain & in stink gland.
In case b (mutant), ATG which is a start codon present in DNA at exon 1. So, it will start transcribe in both brain & stink gland. TAA codon is also present in exon 1 which is a stop codon. So, in this case in both brain & stink gland mRNA transcript will not be present as required exons of 2A, 2B & 3 will be unable to transcribe due to encounter of premature stop codon.
In case c (mutant), ATG which is a start codon present in DNA at exon 1. So, it will start transcribe in both brain & stink gland. TAG codon is present in exon 2B which is a stop codon. In this case though stop codon is present after exon 2A & at exon 2B but present before the exon 3 which is required for both brain & stink gland. So, in this case also mRNA transcript will not be present in both brain & stink gland as required exons 3 will be unable to transcribe due to encounter of premature stop codon.
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