How can a table of mRNA codons and amino acids help deduce the amino acid sequence from a known mRNA base sequence?

Sourav PanNovember 8, 2024

Answered

A table of mRNA codons and their corresponding amino acids is an essential tool for deducing the amino acid sequence from a known mRNA base sequence. Here’s how this process works:

Understanding Codons

1. Codon Definition: Codons are sequences of three nucleotides in mRNA that specify a particular amino acid or a stop signal during translation. For example, the codon AUG codes for methionine, which is also the start codon for protein synthesis.
2. Total Combinations: Since there are four different nucleotides (adenine [A], uracil [U], cytosine [C], and guanine [G]), the combination of three nucleotides allows for 64 possible codons (4^3). This redundancy means that multiple codons can code for the same amino acid, which is an important aspect of the genetic code.

Using the Codon Table

1. Structure of the Table: The genetic code table is typically organized to show all possible codons. Each row and column corresponds to specific nucleotide positions, allowing users to easily find which amino acid corresponds to a given codon.
2. Deducing Amino Acids:
   • To determine the amino acid sequence from an mRNA sequence, one first needs to divide the mRNA sequence into codons by grouping the nucleotides in sets of three.
   • Each codon is then looked up in the genetic code table to find its corresponding amino acid. For example, if the mRNA sequence is 5′-AUG-UUC-GAA-3′, you would translate it as follows:
     • AUG → Methionine (Met)
     • UUC → Phenylalanine (Phe)
     • GAA → Glutamic Acid (Glu)
3. Example Process:
   • Given an mRNA sequence: 5′-AUG UUC GAA UAA-3′
   • Break it into codons: AUG | UUC | GAA | UAA
   • Using the codon table:
     • AUG → Methionine
     • UUC → Phenylalanine
     • GAA → Glutamic Acid
     • UAA → Stop codon (signals termination)

Importance of tRNA

• Role of tRNA: Transfer RNA (tRNA) molecules facilitate this process by bringing the appropriate amino acids to the ribosome based on their anticodons, which are complementary to the mRNA codons. This ensures that each amino acid is added in accordance with the genetic instructions encoded in the mRNA.