The characteristics features of genetic code are
i. It is always universal
ii. It is triplet of nucleotides bases corresponding to 20 amino acids
iii. It is non-overlapping, non-ambiguous and comma

Question

The characteristics features of genetic code are
 i. It is always universal
 ii. It is triplet of nucleotides bases corresponding to 20 amino acids
 iii. It is non-overlapping, non-ambiguous and commaless
 iv. It has start and stop codon
Which of the statements given above are true?

UnlockIAS · Accepted Answer

Correct — D, all four statements are true, so the answer is 'All of the above'. (i) The code is (near-)universal — the same codons specify the same amino acids in almost every organism, from bacteria to humans. (ii) It is a triplet code — each amino acid is read as a group of three nucleotide bases (a codon); the 64 possible codons together specify the 20 standard amino acids. (iii) It is non-overlapping (each base is read only once), non-ambiguous/unambiguous (one codon codes for only one amino acid) and commaless (read continuously with no gaps). (iv) It has one start codon (AUG) and three stop codons (UAA, UAG, UGA). For NCERT/exam purposes universality is treated as a defining feature, so the commission's key counts every statement as correct.

Why the other options are wrong — (a) Leaves out statement (iii) — the code IS non-overlapping, unambiguous and commaless — so this option is incomplete.  (b) Omits statement (ii), the triplet-code fact (3 bases per codon for 20 amino acids), which is true — so it is incomplete.  (c) Omits statement (iv) — the code does have a start codon (AUG) and stop codons (UAA/UAG/UGA) — so it is incomplete.

Concept: The genetic code is the set of rules by which the four-letter nucleotide sequence of mRNA is translated into the 20-amino-acid language of proteins. Bases are read three at a time (codons); with 4 bases there are 4x4x4 = 64 codons for 20 amino acids, so most amino acids have more than one codon — this redundancy is called degeneracy.

State PCS 2020 Q46 — Science & Technology PYQ with Answer

State PCS 2020 Q46 — Science & Technology PYQ with Answer