Question

Howard is explaining the process by which DNA determines the structure of proteins. His explanation includes this statement. "The base pair sequence of a gene determines the sequence of amino acids in a protein." Howard's teacher evaluates this statement, and her critique is that the statement is not accurate in all circumstances. Which feature of gene expression provides the strongest evidence for the teacher's critique?

Answer 1

Answer:

Transcription and RNA processing (splicing)

Explanation:

Although Howard is almost right, the DNA sequence does not precisely relate to the protein sequence. First of all, the DNA is transcribed to an primary mRNA molecule. Bur before the mRNA is ready to be translated into an amino acid sequence, it must be processed into a mature mRNA.

This includes adding a 3' poly A tail, and a 5' cap, and importantly for this question, splicing.

Splicing is the removal of non protein coding intermediate sequences called introns from the protein coding regions (exons) of a primary mRNA. This means that lots of the DNA sequence is not dictated by the final protein, as many of the intervening sequences have been removed by splicing.