Question

Sydney Brenner argued that the code was nonoverlapping because he considered that coding restrictions would occur if it were overlapping. A second major argument against an overlapping code involved the effect of a single nucleotide change. In an overlapping code, how many adjacent amino acids would be affected by a point mutation? In a nonoverlapping code, how many amino acid(s) would be affected?

Short answer

Answer: In overlapping genetic codes, a point mutation potentially affects two adjacent amino acids. In nonoverlapping genetic codes, a point mutation affects only one amino acid.

Step-by-step solution

Define overlapping and nonoverlapping codes

In a genetic code, the codons are sequences of three nucleotides. The difference between overlapping and non-overlapping codes lies in how contiguous codons are organized in the gene. - In an overlapping code, a single nucleotide can be a part of two or more codons. - In a nonoverlapping code, each nucleotide belongs to only one codon, and codons are read consecutively, without overlap.

Determine the effect of a point mutation on overlapping code

In an overlapping code, a single nucleotide change in any of the codons will impact both the codon where the mutation occurred, as well as any adjacent codons that share the mutated nucleotide. Thus, if we have the sequence "ABCDEF" where letters represent nucleotides, a mutation in nucleotide "C" would affect both the ABC and CDE codons. Since a single codon corresponds to one amino acid, this means that a point mutation in an overlapping code will potentially affect two adjacent amino acids.

Determine the effect of a point mutation on nonoverlapping code

In a nonoverlapping code, each nucleotide is only a part of a single codon. Therefore, a point mutation will only affect the single codon where the mutation took place. As a result, only one amino acid would be impacted by this mutation.

Answering the questions

In an overlapping code, a point mutation will potentially affect two adjacent amino acids due to nucleotide(s) being shared by adjacent codons. In a nonoverlapping code, a point mutation will affect only one amino acid, as each nucleotide belongs to only one codon.