In a mixed copolymer experiment, messages were created with either 4/5C:1/5A or 4/5A:1/5C. These messages yielded proteins with the following amino acid compositions.

Using these data, predict the most specific coding composition for each amino acid.

Verified step by step guidance

1. Step 1: Understand the experimental setup. Two mixed copolymers were used: one with 4/5 Cytosine (C) and 1/5 Adenine (A), and the other with 4/5 Adenine (A) and 1/5 Cytosine (C). These mixtures were used to synthesize proteins, and the amino acid yields were measured.
2. Step 2: Analyze the amino acid yields for each copolymer. For each amino acid, compare the yield from the 4/5C:1/5A mixture to the yield from the 4/5A:1/5C mixture. Amino acids with high yield in the 4/5C:1/5A mixture and low yield in the 4/5A:1/5C mixture are likely coded by codons rich in Cytosine. Conversely, amino acids with high yield in the 4/5A:1/5C mixture and low yield in the 4/5C:1/5A mixture are likely coded by codons rich in Adenine.
3. Step 3: For amino acids with similar yields in both mixtures (like Threonine), infer that their codons likely contain a balanced or mixed composition of C and A, or that the codon position being tested is not specific to either base.
4. Step 4: Use the relative yields to predict the most specific coding composition for each amino acid. For example, Proline has a high yield (63.0%) in the 4/5C:1/5A mixture and very low (3.5%) in the 4/5A:1/5C mixture, suggesting Proline codons are rich in Cytosine. Lysine shows the opposite pattern, indicating codons rich in Adenine.
5. Step 5: Summarize the predictions by assigning each amino acid to the base composition (C or A) that corresponds to its higher yield, thus identifying the most specific coding composition for each amino acid based on the experimental data.

Key Concepts

Mixed Copolymer Experiment

A mixed copolymer experiment involves synthesizing RNA sequences with known ratios of nucleotides to determine which amino acids are encoded by specific nucleotide combinations. By analyzing the resulting protein composition, researchers can infer the codon assignments for amino acids based on the frequency of nucleotides in the RNA.

Codon-Amino Acid Specificity

Codon specificity refers to the relationship between a sequence of three nucleotides (codon) in mRNA and the amino acid it encodes. In mixed copolymer experiments, the relative abundance of amino acids produced from different nucleotide ratios helps identify which codons correspond to which amino acids, revealing the genetic code.

Interpreting Amino Acid Yield Data

Amino acid yield data from mixed copolymer experiments show the percentage of each amino acid produced under different nucleotide ratios. High yield of an amino acid in one mixture and low in another suggests that the amino acid is encoded by codons rich in the predominant nucleotide of that mixture, allowing prediction of codon composition.