To answer the questions, let's start with the first one about the amino acid sequence derived from the mRNA sequence CGU-AGA-UUU.
Question 1
- CGU encodes the amino acid Arginine (Arg).
- AGA also encodes the amino acid Arginine (Arg).
- UUU encodes the amino acid Phenylalanine (Phe).
Putting these together, the amino acid sequence for the mRNA CGU-AGA-UUU is Arg-Arg-Phe.
Question 2
Next, to determine which DNA mutation causes the biggest change to the encoded protein, we look at the amino acids encoded by the changes:
- GAA 🡪 GAG: Both encode Glutamic acid (Glu). No change.
- GAA 🡪 GAT: GAA encodes Glutamic acid (Glu); GAT encodes Aspartic acid (Asp). This is a missense mutation that changes one amino acid.
- GAA 🡪 GAC: GAA encodes Glutamic acid (Glu); GAC also encodes Aspartic acid (Asp). This is the same change as the previous case (still a missense mutation).
- GAA 🡪 CAA: GAA encodes Glutamic acid (Glu); CAA encodes Glutamine (Gln). This is also a missense mutation that changes one amino acid.
Among these options, both mutations GAA 🡪 GAT and GAA 🡪 CAA result in a change of amino acid, but the change to a completely different amino acid from Glu to Asp (GAA to GAT) or Glu to Gln (GAA to CAA) illustrates that both are significant changes. However, assuming the question is looking for the biggest impact based on different properties of the resultant amino acids (polar, charged, etc.), the mutation GAA 🡪 CAA (Glu to Gln) is often considered to have a larger impact than GAA to GAT because they change from an acidic amino acid (Glu) to a neutral one (Gln).
Final Responses
- Question 1: Arg-Arg-Phe
- Question 2: GAA 🡪 CAA (the biggest change in terms of charge).
If we focus merely on the different nature of the amino acids, GAA 🡪 GAT causes a bigger functional change, but if the question is about the nature of the amino acids, both can be considered significant.