Question

Terminating or stop codons are

• A. UAA, UGA, UGG
• B. UAA, UAG, UGA
• C. UAG, UUU, UGG
• D. UAA, UAG, UGG

Hint:

Use these mnemonics to remember the stop codons easily:
- U Are Away (UAA)
- U Are Gone (UAG)
- U Go Away (UGA)

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The genetic code is a set of three-nucleotide sequences called codons that specify which amino acid will be added next during protein synthesis.
While most codons specify amino acids, a few codons signal the termination of translation.

Step 2: Detailed Explanation:
During translation, ribosomes read mRNA in the 5'-to-3' direction, assembling amino acids into a polypeptide chain.
When the ribosome encounters a stop codon, translation stops because there are no transfer RNA (tRNA) molecules with complementary anticodons for these sequences.
Instead, release factors bind to the stop codons in the ribosomal A-site, triggering the hydrolysis of the ester bond linking the finished polypeptide chain to the tRNA.
The three standard termination codons in the universal genetic code are:
1. UAA (historically called the ochre codon)
2. UAG (historically called the amber codon)
3. UGA (historically called the opal codon)
The remaining codons mentioned in the options, such as UGG (which codes for Tryptophan) and UUU (which codes for Phenylalanine), are sense codons that specify amino acids.

Step 3: Final Answer:
Therefore, the correct stop codons are UAA, UAG, and UGA, corresponding to option (B).