Which Of The Following Is NOT A Stop Codon? A UAG UAC UAA UGA All Are Stop Codons
The correct answer and explanation is:
Correct Answer: UAC
Explanation:
In genetic coding, stop codons play a crucial role in signaling the termination of protein synthesis during translation. There are three recognized stop codons in the standard genetic code:
- UAG (Amber)
- UAA (Ochre)
- UGA (Opal)
These codons do not correspond to any amino acid and are recognized by release factors in the ribosome, leading to the disassembly of the translation complex and the release of the newly synthesized protein.
Why is UAC NOT a Stop Codon?
Unlike UAG, UAA, and UGA, UAC actually codes for an amino acid rather than stopping translation. UAC is a codon for Tyrosine (Tyr), an essential amino acid used in protein synthesis. It does not signal termination and allows ribosomes to continue elongating the polypeptide chain.
The Importance of Stop Codons
Stop codons ensure that proteins are synthesized accurately and terminate at the correct point. Without them, proteins could be improperly formed, leading to potential malfunctioning within cells. Mutations that affect stop codons can result in incomplete or excessively long proteins, which may cause genetic disorders or diseases such as cancer.
Summary
- UAG, UAA, and UGA → Stop codons (signal termination of translation)
- UAC → NOT a stop codon; codes for the amino acid Tyrosine
- All are NOT stop codons is incorrect, because UAC is not a stop codon.
Thus, UAC is the correct answer as it is not a stop codon.