Question

mRNA that carries information for complete polypeptide synthesis is

• A. Muton
• B. Codon
• C. Operon
• D. Reading frame

Answer 1

The correct option is D Reading frame

An operon consists of the gene cluster, promoter and other regulatory sequences that function together in regulation of transcription; option A is incorrect. Codon is a set of three nucleotides that code for an amino acid; it does not code for the whole polypeptide. mRNA nucleotide sequence is read in codons which in turn determine the type and sequence of amino acids in synthesizing polypeptides. Mucons are the smallest unit of mutation of a gene; a recon consists of one to several muton. A stretch of mRNA that carries information for polypeptide synthesis constitutes reading frame. Any given mRNA sequence can have three possible reading frames each of which gives a different sequence of codons. A specific first codon in the sequence determines the reading frame, in which a new codon begins every three nucleotide residues. For example, a DNA sequence “AAAGGGTTTCCC” can have three possible reading frames:

1. “AAA’GGG’TTT’CCC”,

2. “A’AAG’GGT’TTC’CC” and

3. “AA’AGG’GTT’TCC’C”.

Therefore, the correct answer is option D.