Question

6. Which of the following mutations would most likely have the severest consequences: Explain your reasoning. a. A change in amino acid recognition of an aminoacyl-tRNA synthetase b. A frame shift mutation at the end of the coding sequence of a gene A mutation at a splice junction C.

Answer 1

The most severe consequences among the given mutations will be from c. mutation at a splice junction. This is due to the given reasons:

c. Mutation at a splice junction will result in either the removal of whole exon or retention of the whole intron in the mRNA sequence, causing formation of non-functional protein.

DNA Exon 1 Intron Exon 2 Intron Exon 3 DNA Exon 1 Intran Exon 2 Intron Exon 3 Altered mRNA Exon1 Exon 2 Exon 3 Altered mRNA Exon 1 Exan 3

^{Image adapted from: https://en.wikipedia.org/wiki/Splice_site_mutation}

Splice-site mutations have been also found to have implications in several disorders like dementia, Cancer, Epilepsy etc.

While,

a. Change in the amino acid recognition by aminoacyl tRNA synthetase will result in the incorporation of an incorrect amino acid during the translation process.

b. Frameshift mutations result in the formation of entirely different protein due to deletion or insertion of a new base pair in the DNA sequence.

ATGCCTGGTTATGA TACG GACCAATACT Altered reading frame 分 Insertion ATGC CIGTTATGA TACGGACA ATACT Normal reading frame Deletion ATGCCGTTATGA TA CGG CA ATACT Altered reading frame

^{Image adapted from http://utminers.utep.edu/rwebb/html/what_is_a_mutation_.html}

But as it is mentioned that, it happens at the end of the coding sequence of a gene, It doesn't lead to very severe consequences as the frameshift mutation caused in the beginining or the middle of gene.