Question

When the amino acid sequences of insulin isolated from different organisms were determined, some differences were noted. For example, alanine was substituted for threonine, serine was substituted for glycine, and valine was substituted for isoleucine at corresponding positions in the protein. List the single-base changes that could occur in triplets to produce these amino acid changes.

Short answer

Answer: The possible single-base changes in the codons that produce the given amino acid substitutions are as follows: 1. Alanine (Ala) to Threonine (Thr): GCU to ACU, GCC to ACC, GCA to ACA, GCG to ACG 2. Serine (Ser) to Glycine (Gly): UCU to GCU, UCC to GCC, UCA to GCA, UCG to GCG, AGU to GGU, AGC to GGC 3. Valine (Val) to Isoleucine (Ile): GUU to AUU, GUC to AUC, GUA to AUA, GUG to ACG (Not a perfect match, but the closest for the given exercise)

Step-by-step solution

Identifying the codons for each amino acid

For this step, we need to refer to the genetic code table to find the codons corresponding to the mentioned amino acids. Here are the respective codons: Alanine (Ala, A): GCU, GCC, GCA, GCG Threonine (Thr, T): ACU, ACC, ACA, ACG Serine (Ser, S): UCU, UCC, UCA, UCG, AGU, AGC Glycine (Gly, G): GGU, GGC, GGA, GGG Valine (Val, V): GUU, GUC, GUA, GUG Isoleucine (Ile, I): AUU, AUC, AUA

Identifying possible single-base changes in the codons

Now, we will determine the possible single-base changes for each of the given amino acid substitution pairs that would result in a different amino acid. Alanine -> Threonine: GCU -> ACU GCC -> ACC GCA -> ACA GCG -> ACG Serine -> Glycine: UCU -> GCU UCC -> GCC UCA -> GCA UCG -> GCG AGU -> GGU AGC -> GGC Valine -> Isoleucine: GUU -> AUU GUC -> AUC GUA -> AUA GUG -> ACG (Not a perfect match, but the closest for the given exercise)

Summarize the single-base changes

The possible single-base changes in the codons that produce the given amino acid substitutions are as follows: Alanine (Ala) to Threonine (Thr): GCU to ACU, GCC to ACC, GCA to ACA, GCG to ACG Serine (Ser) to Glycine (Gly): UCU to GCU, UCC to GCC, UCA to GCA, UCG to GCG, AGU to GGU, AGC to GGC Valine (Val) to Isoleucine (Ile): GUU to AUU, GUC to AUC, GUA to AUA, GUG to ACG (Not a perfect match, but the closest for the given exercise)