Question

In a mixed copolymer experiment, messages were created with either \(4 / 5 \mathrm{C}: 1 / 5 \mathrm{A}\) or \(4 / 5 \mathrm{A}: 1 / 5 \mathrm{C}\). These messages yielded proteins with the following amino acid compositions. Using these data, predict the most specific coding composition for each amino acid.

Short answer

Answer: To determine the most specific coding composition for each amino acid, analyze the amino acid composition data of Protein 1 and Protein 2. Amino acids present in higher proportion in Protein 1 are most likely coded by C's, while amino acids present in higher proportion in Protein 2 are most likely coded by A's.

Step-by-step solution

Understand the given information

The two messages have different compositions: one has a ratio of 4 parts C to 1 part A, while the other has the opposite ratio, 4 parts A to 1 part C. The proteins produced by these messages have different amino acid compositions. We'll call them Protein 1 and Protein 2.

Identify the pattern in the message composition

We can see that the ratio between C and A in the two messages is the same but reversed. In the first message, there are more C's than A's, while in the second message, there are more A's than C's.

Relate the message composition to the amino acid composition

Since there are more C's in the first message, and fewer A's, we can infer that the amino acid composition of Protein 1 resulted primarily from C's contribution. Similarly, since there are more A's in the second message and fewer C's, the amino acid composition of Protein 2 resulted primarily from A's contribution.

Predict the coding composition for each amino acid

Based on our analysis, we can predict the coding composition for each amino acid as follows: - For the amino acids present in higher proportion in Protein 1, they are most likely coded by C's. - For the amino acids present in higher proportion in Protein 2, they are most likely coded by A's. By analyzing the amino acid composition data and comparing the proportions for each protein, we can identify which amino acids are likely coded by C and A.

Key concepts

Understanding Amino Acid Composition

The building blocks of proteins are amino acids, each with unique characteristics influencing the function and structure of the final protein. When decoding genetic information, scientists look at the amino acid composition of proteins as a direct reflection of the underlying genetic messages. In the context of the copolymer experiment mentioned in the exercise, identifying the amino acid composition is essential to infer which nucleotides code for which amino acids.

Each set of three nucleotides, known as a codon, corresponds to a specific amino acid. The arrangement of these nucleotides determines which amino acids will be produced and in what quantity. By analyzing the data from the experiment — the proportions of amino acids in Protein 1 and Protein 2 — it's possible to hypothesize which nucleotides are responsible for the coding of specific amino acids.

For example, if a particular amino acid is more abundant in Protein 1, which was generated from a message with a higher ratio of cytosine (C), it suggests that cytosine is likely part of the codon for that amino acid. Conversely, if an amino acid is found in greater quantities in Protein 2, from a message with more adenine (A), adenine likely plays a critical role in that amino acid's codon. Understanding these relationships helps unlock the code that governs how proteins are constructed from genetic blueprints.

Deciphering the Code with a Copolymer Experiment

The copolymer experiment is a scientific method for studying genetic codes. In these experiments, synthetic messages are created with known ratios of nucleotides. The resulting proteins are then analyzed to determine the amino acid composition (as is described in the exercise). By doing so, scientists can gain insights into which nucleotides are involved in the coding of specific amino acids.

In the exercise, two copolymers were created with complementary nucleotide ratios: one with cytosine (C) being more prevalent and the other with adenine (A) dominating. The different amino acid compositions of the proteins produced by these messages are a tell-tale sign of the specific interactions between certain nucleotides and amino acids.

Conducting an experiment such as this allows for a hands-on approach to understanding the genetic code. By varying the nucleotide ratios and observing the corresponding changes in amino acid composition, researchers can deduce the most likely genetic codes for each amino acid, building a more detailed picture of how genetic information is translated into functional proteins.

Nucleotide Ratios and Genetic Coding

Nucleotides are the molecular units that make up DNA and RNA, serving as the alphabet of the genetic code. Each nucleotide contains one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T), with uracil (U) replacing thymine in RNA. The ratios in which these nucleotides occur in a genetic sequence can provide vital clues to the structure and function of the encoded proteins.

The exercise you're studying involves analyzing the effects of different nucleotide ratios on protein synthesis. Specifically, the ratios are 4/5 C to 1/5 A and the inverse, 4/5 A to 1/5 C. These ratios influence the probability of certain amino acids being encoded during protein synthesis. As the ratio suggests a predominance of one nucleotide over the other, the amino acids that are encoded by the more abundant nucleotide will occur more frequently in the produced protein.

By exploring how changes in the nucleotide ratio affect the amino acid composition, scientists can start to piece together which nucleotides are responsible for coding each amino acid in the genetic code. This understanding is foundational to fields such as genetics, molecular biology, and bioinformatics, as it allows for the prediction of protein structures based on genetic sequences — a critical aspect of both basic biological research and the development of new medical treatments.