Question

Can you please help me with this problem:

3. A dominant wild-type allele D produces full enzyme function, but a recessive alleled, produces no functional enzymatic action, and a recessive allele da produces reduced enzyme function. Western blot analysis of the proteins produced by organisms with different genotypes for this gene gives the results shown. Note, proteins separate out in a gel by size similar to DNA fragments with smaller polypeptides traveling farther. Genotype DD Dd, Dd, dod, dd₂ d₂d₂ a. What kind of protein change might result in two western blot bands for organisms with the Dd2 genotype? (1 pt) b. What might explain the absence of detectable protein for organisms with the didi genotype? (1 pt) c. Why might there be just one protein band for organisms with the d7d2 and dad 2 genotypes? (1 pt) d. Based upon your assessment of the western blot analysis, speculate about the nature of the mutations producing di and d. In other words, what has happened at the DNA level to produce these mutations? (up to 2 pts)

Answer 1

a. D = WT allele that produces the full-length functional protein
d2 = Mutant allele that produces a truncated protein with reduced function
So, there are two bands in the Dd2 lane

b. d1 could be a null allele
i.e. there is no transcription/translation of the d1 allele

c. d1 allele does not produce any band
So,
d1d2 = A single band corresponding to the d2 allele
d2d2 = A single band corresponding to the d2 allele

d. d2 = A premature stop codon due to a nonsense mutation at the 3'-region of the gene
d1 = A mutation in the promoter sequence