Question

Researchers compared the amino acid sequences of the transport protein in zebra fish, puffer fish, mice, and humans. They found many stretches with identical sequences in all four species. Does this mean that the corresponding mRNA base sequences are also the same in these four species? Explain why or why not.

Answer 1

No

Step-by-step explanation:

The genetic codes in mRNA are organized into codons - a sequence of 3 nucleotides that codes for amino acids. There are 4 bases in nature and as such there are
`4^3` possible codons in nature.

However, there are only 20 amino acid in nature and they are being coded for by 64 codons. It thus means that an amino acid can be coded for by multiple codons. This is why codons are said to be degenerates.

For example, the amino acid alanine is coded for by GCU, GCC, GCA, GCG. Hence, having the same amino acid sequence does not necessarily mean that mRNA sequence will be the same.