2) When a fifth defenseless mutant, df-5, was isolated in a subsequent screen, i

Question

2) When a fifth defenseless mutant, df-5, was isolated in a subsequent screen, its phenotype was found to be identical to dn-4 (ie, it could be rescued by either PMA-B or PMA-C, but not with PMA-A). However, further genetic analysis (specifically, a complementation test) indicated that the dfl-4 and dfl-5 mutations affect two different genes. Which of the following is NOT a reasonable explanation that could account for this result? (i.e, for why mutations in different genes might appear to have the same effect on the pathway?) a) The step affected by the two mutations might normally be carried out by an enzyme with two different subunits with one polypeptide encoded by adfl-4 and the other by df-5. b) There might be two different (but fiunctionally-equivalent) enzymes that can catalyze the same step, with one enzyme encoded by dfl-4 and the other by dfl-5 o) One of the genes (eg.dn-5) might encode a transcription factor or other regulatory protein that is needed for expression of the other gene (e.g., dfi-4) d) There might be an additional, fifth step in the pathway (and also a fourth, "unknown" PMA/intermediate) that is normally catalyzed by the df1-5 gene product, and which occurs just before or just after the "df-4" step e) None of the above (i e, all are reasonable explanations for the similar behavior of dl-4 and Answer (continued on other side)

Explanation / Answer

Right answer should be e) none of the above is not a reasonable answer because all the 4 explantions mechanism may be possible to look phenotypically same but genetypically different.

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