Question

Most proteins have more leucine than histidine residues but more histidine than tryptophan residues. Correlate the number of codons for these three amino acids with this information.

Short answer

Answer: The number of codons for each amino acid directly correlates with their occurrence in proteins. Leucine has more codons (6) than both histidine (2) and tryptophan (1), which means leucine is more likely to be present in protein sequences. Similarly, histidine has more codons (2) than tryptophan (1), making histidine more common in proteins than tryptophan.

Step-by-step solution

Determine the Genetic Code of Leucine, Histidine, and Tryptophan

First, we need to search for the genetic code of these three amino acids. This information can be found in a genetic code table. Upon checking the table, we find that: - Leucine (Leu, L): 6 codons (UUA, UUG, CUU, CUC, CUA, CUG) - Histidine (His, H): 2 codons (CAU, CAC) - Tryptophan (Trp, W): 1 codon (UGG)

Compare the Number of Codons

Now that we know the number of codons for each amino acid, we can compare them: Leucine has more codons (6) than both histidine (2) and tryptophan (1). This means that there is a higher chance that leucine will be present in the protein sequence. Histidine also has more codons (2) than tryptophan (1), so histidine is expected to occur more often than tryptophan in a protein sequence.

Correlate the Codon Numbers with the Information Given

The information given stated that most proteins have more leucine than histidine residues and more histidine than tryptophan residues. Based on the number of codons we found for each amino acid, this holds true: Leucine (6 codons) > Histidine (2 codons) > Tryptophan (1 codon). This means that the number of codons for each of the three amino acids directly correlates with their occurrence in proteins.

Key concepts

Amino Acids

Amino acids are the building blocks of proteins. They serve many roles and without them, cells couldn't survive. There are 20 different amino acids that make up proteins in living organisms. Each amino acid differs in its chemical structure, specifically the side chain, which can confer different properties, such as being polar, non-polar, charged, etc.
In this context, amino acids such as leucine, histidine, and tryptophan are important because they appear frequently in proteins. However, the likelihood of their occurrence is influenced by the number of codons available to encode them.

• Leucine: Has 6 codons, making it more likely to appear frequently in proteins.
• Histidine: With 2 codons, it still appears more often than tryptophan.
• Tryptophan: Only has 1 codon, making it the least frequent among the three in proteins.

Understanding the roles of these amino acids and the frequency at which they appear helps decipher the complex processes of protein synthesis.

Codons

Codons are sequences of three nucleotides in mRNA that dictate the addition of specific amino acids to a growing protein during translation. Each group of three nucleotides, or codon, corresponds to a single amino acid or a stop signal during the protein synthesis process. This relationship is defined by the genetic code.
The genetic code is universal and nearly the same in all organisms, which speaks to its evolutionary importance. In the genetic code table, leucine, histidine, and tryptophan are encoded by specific codons.

• Leucine Codons: UUA, UUG, CUU, CUC, CUA, CUG. Due to having six codons, leucine is frequently expressed.
• Histidine Codons: CAU, CAC. With only two codons, histidine appears less frequently, yet more than tryptophan.
• Tryptophan Codon: UGG, with only one codon, makes it less common.

These codons highlight why certain amino acids appear more than others in proteins, affecting protein structure and function.

Protein Sequence

The sequence of amino acids in a protein determines its structure and function. Proteins are essentially long chains of amino acids strung together in a specific order, analogous to letters forming specific words. The order of amino acids is dictated by the order of codons in the mRNA sequence.
Having a greater number of codons for a particular amino acid increases its chance of appearing more frequently in the protein sequence. For example, with six codons, leucine is a regular component of proteins, while tryptophan, with only one codon, occurs far less often.

• A single amino acid change can dramatically alter a protein's function, demonstrating the importance of precise amino acid sequencing.
• Protein sequences can be optimized over time through evolution to perform specific functions more efficiently.

Hence, understanding the protein sequence and its codons can offer insights into protein function and its evolutionary adaptation.