Question

A single point mutation in a gene results in a nonfunctional protein. Individuals heterozygous for this mutation were identified using a Southern blot. Which pair of wild-type (WT) and mutant alleles most likely contains the mutation?

A. WT 5-TAGTCGAAGCTTAGGCATCT-3
Mutant 5-TAGTCGATGCTTAGGCATCT-3
B. WT 5-TAGTCGAAGCTTAGGCATCT-3
Mutant 5-TAGTCGAAGCTTAGGCATAT-3
C. WT 5-TAGTCGAAGCTTAGGCATCT-3
Mutant 5-TAGTTGAAGCTTAGGCATCT-3
D. WT 5-TAGTCGAAGCTTAGGCATCT-3
Mutant 5-TAGTCCAAGCTTAGGCATCT-3

Answer 1

C. WT 5-TAGTCGAAGCTTAGGCATCT-3

Mutant 5-TAGTTGAAGCTTAGGCATCT-3

Step-by-step explanation:

In the wild type, the DNA sequence encodes the following aminoacidic segment: SRSLGI; while the mutant form has a stop codon in the second codon (TGA). A stop codon is a trinucleotide sequence in the messenger RNA (mRNA) that indicates a stop signal in protein synthesis. There are three types of stop codons: UGA, UAG and UAA, where U represents Uracile in the mRNA instead of Thymine in the DNA sequence.

Representation:

C. WT 5-T AGT CGA AGC TTA GGC ATC T-3 >> 5'3' Frame 1 = SRSLGI

Mutant 5-T AGT TGA AGC TTA GGC ATC T-3 >> 5'3' Frame 1 = S-, where - represents a stop codon (TGA) and therefore it is the end of the protein.