Question

12.) Compare the consequences of an error made in (i) the synthesis of a molecule of a polypeptide, (ii) the transcription of a molecule of mRNA, and (iii) the replication of a sense strand of a transcriptional unit that gives rise to a molecule of mRNA. Which of these three types of errors is potentially heritable?

Answer 1

Consequences of error made in

(i) the synthesis of a molecule of a polypeptide

Since a polypeptide s a long polymer of amino acids and particular sequence of a polypeptide gives that polypeptide a native function. If an error made during synthesis of a molecule of a polypeptide most probably the polypeptide will lose its native function but again it may or may not become non-functional (depending upon how costly the error is i.e. whether the change due to error is sequential, structural and/or functional). Therefore, one thing is clear that due to the error the polypeptide that is generated will not be the original or native one.

(ii) the transcription of a molecule of mRNA

Since the mRNA sequence determines the polypeptide sequence thus if there is an error in the transcription of a molecule of mRNA then the mRNA sequence changes which in turn changes the polypeptide sequence as a result the polypeptide may or may not become non-functional (depending upon how costly the error is i.e. whether the change due to error is sequential, structural and/or functional) but one thing is sure the polypeptide will not be the same native or wild-type one.

(iii) the replication of a sense strand of a transcriptional unit that gives rise to a molecule of mRNA

Again, this sense strand gives rise to the molecule of mRNA. So, any change will cause a change in mRNA and as discuss above there will be change in polypeptide sequence, structure and/or function depending upon the error.

Since, it is DNA which is heritable from prokaryotes to eukaryotes. Thus, the error that will occur in the (iii) the replication of a sense strand of a transcriptional unit that gives rise to a molecule of mRNA is potentially heritable.