Genetics Question

[kryptonxenon]

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This is from TBR Bio:

Which of the following statements is LEAST likely to result from gene duplication?
A. Synthesis of similar amino acid sequences
B. Synthesis of similar tRNA sequences
C. Independent mutation of the DNA sequences
D. Synthesis of longer mRNA sequences

The answer to this question is D. I figured that if gene duplication occurs, you get more base pairs in DNA and thus a longer mRNA sequence. However, this isn't what is actually happening. Why are A, B, and C incorrect? And why is D correct?

 

[laczlacylaci]

Have you figured this out?

 

[sharpstickie]

I know this is late, but when you said
"I figured that if gene duplication occurs, you get more base pairs in DNA and thus a longer mRNA sequence."
You're assuming that the DNA chain is getting longer, but the gene duplication referenced here is within mitosis where the chromosomes are being duplicated. Changing what the question is asking then only leaves D to be LEAST likely. It is unlikely that mRNA sequences will be extended because you're assuming the DNA is nearly identical.

 

[wizzed101]

Uhm.... I believe that gene duplication here refers to an evolutionary mechanism. The idea is that if you have 2 copies of a same gene on different chromosomes, you can either die or survive. If you survive, you have more room for errors in experimenting with genetic evolution: the original gene can be either deleted, mutated, or regulated differently. The outcomes lead to new chromosomes.

And besides, each gene has it own regulatory sequences including start and stop signal for mRNA. To elongate the mRNA, the insertion has to be pretty specific.

 

[kryptonxenon]

I know this is late, but when you said
"I figured that if gene duplication occurs, you get more base pairs in DNA and thus a longer mRNA sequence."
You're assuming that the DNA chain is getting longer, but the gene duplication referenced here is within mitosis where the chromosomes are being duplicated. Changing what the question is asking then only leaves D to be LEAST likely. It is unlikely that mRNA sequences will be extended because you're assuming the DNA is nearly identical.

Thank you @bon22. That makes sense. If a gene is duplicated on a chromosome will it form two adjacent copies on the same chromosome?