10. Conditional alleles are mutant gene versions encoding proteins that can func
ID: 266793 • Letter: 1
Question
10. Conditional alleles are mutant gene versions encoding proteins that can function normally at the permissive condition but are defective at the restrictive condition. One commonly used condition is temperature. Conditional alleles are especially useful to geneticists because they permit the study of essential genes. At the permissive temperature, the organism lives normally. When the organism is shifted to the non-permissive temperature, the effect of inactivating the gene can be studied. Which of the alleles shown below (mutations are bold and underlined) is most likely to lead to a conditional allele? Full to a conditional allele. Assume that the coding region of the mRNA is 1000 codons, but only the first few codons having mutation(s) are shown. y explain your choice, indicating why each of the other choices may not lead -AUG GCU UGG AUC GAC- -AUG GCU UGA AUC GAC- -AUG GCU UGG AUA GAC- -AUG GCU UGG AUC GAG- AUG GCU UGG AAU CGA C wild-type allele 1 allele 2 allele 3 allele 4 @U C A G?UC/AG GU Valine A Arginne A C Leucine Serne U A d ACU? GACUExplanation / Answer
Solution:
Allele 1: It has a mutation resulting in a stop codon (UGA). So this would not code for a functional gene.
Allele 2: It has a silent mutation. So this would code for the same amino acid (i.e. Isoleucine)
Allele 3: It has a missense mutation resulting in a change of amino acid (Aspartic acid to Glutamic acid). So this can change the maturation (folding pattern i.e. secondary or tertiary structure) of the protein. During permissive temperatures this can still retain the functional activity. However during non-permissive temperatures the folding pattern may result in non-functional protein, especially if it is in active site of the protein.
Allele 4: It has an insertion of a nucleotide resulting in frameshift mutation. So this would completely change the amino acid sequence thereby resulting in a non-functional protein.
So the answer would be Allele 3.
Hope this helps.
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