If a mutation changes a complete piece of DNA so that its sequence reads CGACCTCAA instead of CGACCTGAA, which would occur?

Question

The genetic code & codon table (article) | Khan Academy

a
an amino acid deletion resulting in a shorter protein
b
a frameshift mutation resulting in multiple amino acid changes within the protein
c
a base pair substitution resulting in the same protein
d
a point mutation substitution resulting in a different protein

Answer 1

To determine the effect of the mutation that changes the DNA sequence from CGACCTGAA to CGACCTCAA, we will analyze the nature of the mutation and its potential impact on the protein.

1. Identify the change: The mutation involves a single base substitution where 'G' in CGACCTGAA is changed to 'C', changing the sequence to CGACCTCAA.

2. Determine the implications:

   • A base substitution is when one nucleotide in the DNA sequence is replaced by another. In this case, G (guanine) is replaced by C (cytosine).
   • Depending on which base is replaced and what the new base is, this could either lead to a synonymous (no change in amino acid) or nonsynonymous (change in amino acid) effect on the resulting protein.

3. Codon analysis:

   • The original sequence CGACCTGAA, when translated, would correspond to specific codons for amino acids. If we break it down:
     • CGA - Arginine (R)
     • CCT - Proline (P)
     • GAA - Glutamic acid (E)
   • The mutated sequence CGACCTCAA:
     • CGA - Arginine (R)
     • CCT - Proline (P)
     • CAA - Glutamine (Q)

   Here, the last codon changes from GAA (Glutamic acid) to CAA (Glutamine). This means there is a change in the amino acid sequence at the end of the protein.

4. Conclusion: Since this is a substitution that results in a different amino acid being incorporated into the protein, it is a point mutation (single base alteration) that changes the protein sequence.

Thus, the correct option that describes the outcome of the mutation is: d: a point mutation substitution resulting in a different protein.