Question

A novel protein discovered in a certain plant has many leucinerich regions, fewer alanine-rich regions, and even fewer tyrosine residues. Correlate the number of codons for these three amino acids with this information.

Short answer

Short Answer: The number of codons for the amino acids leucine, alanine, and tyrosine is directly correlated with their occurrence in the novel protein. Leucine has the most codons (6), making it more likely to be incorporated into the protein, resulting in leucine-rich regions. Conversely, alanine has fewer codons (4) and tyrosine has the least number of codons (2), causing them to appear less frequently in the protein structure. This correlation exists due to the genetic code's redundancy, which allows multiple codons to code for the same amino acid and provides a level of tolerance for mutations.

Step-by-step solution

Understand the Genetic Code and Codons

The genetic code is a set of rules that specify how the sequence of nucleotide bases in DNA or RNA translates to amino acid sequences in proteins. Each group of three nucleotides is called a codon, and it corresponds to a specific amino acid or a signal for starting or stopping the translation process.

Identify Codons for Leucine, Alanine, and Tyrosine

We need to look up the codons for the three amino acids: leucine, alanine, and tyrosine. The genetic code shows us that: - Leucine (Leu) has 6 codons: UUA, UUG, CUU, CUC, CUA, and CUG. - Alanine (Ala) has 4 codons: GCU, GCC, GCA, and GCG. - Tyrosine (Tyr) has 2 codons: UAU and UAC.

Analyze Codon Redundancy

Notice that leucine has the most codons (6), followed by alanine (4), and finally tyrosine (2). This redundancy is known as 'degeneracy' in the genetic code. It allows multiple codons to code for the same amino acid, providing a certain level of tolerance for mutations.

Correlate Codon Numbers with Amino Acid Occurrence in the Novel Protein

Now, we can correlate the number of codons for these amino acids with the information that the novel protein has many leucine-rich regions, fewer alanine-rich regions, and even fewer tyrosine residues. - Leucine-rich regions: Since leucine has the most codons (6), it has a higher chance of being incorporated into the protein. Hence, numerous leucine-rich regions are observed. - Alanine-rich regions: Alanine has fewer codons (4) than leucine, which means it has less redundancy and a lower probability of being incorporated into the protein. This explains the fewer alanine-rich regions in the novel protein. - Tyrosine residues: Tyrosine has the least number of codons (2), making it even less likely to be incorporated into the protein. This is consistent with the information that there are even fewer tyrosine residues in the novel protein. In summary, the number of codons for leucine, alanine, and tyrosine is directly correlated with their occurrence in the novel protein. The amino acid with the most codons—leucine — is more likely to be incorporated into the protein, resulting in leucine-rich regions, whereas alanine and tyrosine have fewer codons and are less common in the protein.

Key concepts

Codons and Amino Acids

The genetic code is the foundation of biological information transfer from nucleic acids to proteins, working as a translation system. Each amino acid that makes up proteins is encoded by a sequence of three nucleotides known as a codon. For instance, a codon like AUG not only codes for the amino acid methionine, but also serves as the start signal for protein synthesis. When we consider leucine, alanine, and tyrosine, we see that leucine is coded by six different codons, indicating why proteins with leucine-rich regions may be common.

Understanding the relationship between codons and their corresponding amino acids is crucial. There's a specific codon for the start of protein synthesis and three 'stop' codons (UAA, UAG, and UGA) that signal when protein synthesis should end. This beginning-to-end reading frame is essential for creating the correct protein structure. While some amino acids are defined by a single codon, others can have multiple codons, offering insight into the structure and function of proteins found in nature.

Degeneracy of the Genetic Code

When we say that the genetic code is 'degenerate,' we're referring to the phenomenon where multiple codons can code for the same amino acid. This feature of the genetic code provides a buffer against mutations—alterations to the DNA sequence—by allowing synonymous mutations (those that do not alter the amino acid sequence of the protein) to occur without detrimental effects on the protein function.

A look at the redundancy or degeneracy reveals an evolutionary advantage. The ability of six codons to code for leucine, as opposed to only two for tyrosine, illustrates how genetic redundancy can influence protein composition. Mutations in DNA that might otherwise have been harmful can end up benign if they occur within these redundant codon sequences. Moreover, the genetic code being universal among most organisms highlights how critical and conserved these translation rules are for life.

Correlation Between Codon Redundancy and Protein Composition

The exercise example featuring a plant protein with many leucine-rich regions and fewer regions rich in alanine or tyrosine illustrates an intrinsic correlation between codon redundancy and protein composition. The number of codons for each amino acid can influence how often it appears in proteins: the more codons, the higher the chances of that amino acid being included. This is due to the statistical likelihood that multiple codons for an amino acid increase its representation during the translation process.

Leucine, with its six codons, will statistically be more abundant in a random polypeptide chain than tyrosine with just two. This abundance can affect protein structure, function, and even the efficiency of protein synthesis. Ultimately, understanding codon redundancy not only helps us predict protein composition but also offers insight into the intricate mechanisms of genetic regulation and evolutionary biology. Overall, the genetic code's design is a perfect example of nature's intricate balance between flexibility and precision.