Streptomycin resistance in Chlamydomonas may result from...

Question

Streptomycin resistance in Chlamydomonas may result from a mutation in either a chloroplast gene or a nuclear gene. What phenotypic results would occur in a cross between a member of an mt⁺ strain resistant in both genes and a member of a strain sensitive to the antibiotic? What results would occur in the reciprocal cross?

Accepted Answer

Hi, everybody. Let's take a look at this practice problem together. Streptomycin resistance inclement Simonis is acquired through mutations in the. Now, Clem Adamonis is a type of green algae and it can develop resistance to the antibiotic Streptomycin. It does this through mutations but where do those mutations occur? Is it in a, the 16 S are RNA gene B, 18 S R RNA gene C S R RNA gene or D D N A polymerase gene. Now recall that Streptomycin sins mechanism of action is to inhibit protein synthesis and it does this by binding to the ribosomes. So it halts protein synthesis of clement Ramona's. So we can eliminate option D because D N A polymerase is not involved in protein synthesis. Now also recall that our RNA, which is an option in all the rest of our answers is Ribas, omo R N A. So these pieces end up making the ribosomes and the ribosomes and climate. Ramona's are located in chloroplasts. Now, it's the 16 S R RNA gene where the mutation occurs that allows Streptomycin resistance. So A is the correct answer. Now, the mutation in this gene, it alters the structure of that R R N A. What this does is that it prevents Streptomycin from binding the ribosomes and halting protein synthesis. So this mutation allows the ribosome to continue protein synthesis despite Streptomycin presence. So again, the correct answer is a 16 S R RNA gene. Alright. Everyone, I hope you found this helpful and I'll see you soon for the next practice problem.

Key Concepts

Chloroplast and Nuclear Genes

Phenotypic Expression

Reciprocal Crosses

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