Q5.1 If two RNA molecules have complementary base sequences, they can hybridize
ID: 90929 • Letter: Q
Question
Q5.1 If two RNA molecules have complementary base sequences, they can hybridize to form a double-stranded helical structure, just as DNA can. Imagine that, in a par- ticular region of the genome of a certain bacterium, one DNA strand is transcribed to give rise to the mRNA for protein A and the other DNA strand is transcribed to give rise to the mRNA for protein B. a. Would there be any problem in expressing these genes? b. What would you see in protein B if a mutation oc- curred that affected the structure of protein A?Explanation / Answer
Q5.1a) No. There wouldn't be any problem in expressing these genes but, transcription or expresion for a majority of genes use only the sense RNA strand first and the other strand is not transcribed at biologically relevant levels and in any case has no meaning in terms of protein, though both the strands are needed for replication. Hence, the transcription done by the RNA polymerase can use only one of the 2 strands as a template for transcription. The other strand serves as a template at a different instance.
b. If there is a mutation that affected the structure of protein A, there wouldn't be any change in the protein B, because only one strand of the DNA would impart this mutation and the other strand is free to transcribe.
Q6.2) In event 1, The proofreading function identifies copying errors and corrects them. It would introduce mutations during DNA replication and might cause a change in the genetic code. However, if this mostly occurs in the DNA that doesn't encode for a protein so it doesn't have any effect on the protein.
In event 2, if an incorrect nucleotide is inserted into an mRNA during transcription, it would be removed by the DNA polymerase II and if not, there would be a change in the reading frame, or a defective protein would be formed. It may or may not have an overall effect on the structure of the protein to be formed. Either, a truncated or a larger non-functional protein would be formed.
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