Question

Select the incorrect statement(s) about genetic codon.
(i) Six codons do not code for any amino acid.
(ii) Codon is read in mRNA in a contiguous fashion.
(iii) Three codons function as stop codons.
(iv) The initiation codon AUG codes for methionine.
(A) (i) only
(B) (ii) only
(C) (i), (ii) and (iv)
(D) (i), (ii) and (iii)

Answer 1

Hint: The set of instructions utilised by living cells to convert data from genetic material contained in proteins is known as the genetic code. There are two forms of genetic coding. RNA codons or DNA codons can both be used to express the genetic code. Messenger RNA (mRNA) contains RNA codons, which are the codons that are actually "read" when polypeptides are synthesized (the process called translation).

Complete Step by Step Answer:
Genetic code have all the features listed below:
a)The genetic code is comma-free. This indicates that the triplet codons are arranged on m-RNA one after the other without a gap.
b) Clear nature: Each codon designates a certain amino acid. AUG, which codes for methionine, and GUG, which codes for valine, are the only exceptions. However, GUG can also code methionine if AUG is not present.
c)20 amino acids are represented by 61 codons, which is a degenerate nature. However, certain amino acids are encoded by several codons. As a result, it is considered deteriorated. Examples of codes for glycine include GGG, GGA, GGC, and GGU.
d) Polarity: On m-RNA, the genetic information could only be read in the 5'-3'direction. The crucial component of the genetic code is this polarity. Start and stop signals are also present.
The stop codons are three codons that don't code for any amino acids. It's UAG, UAA, and UGA. As a result, statement 1 is untrue. The triplet codon used in genetic code specifies that three RNA bases represent an amino acid. The start codon, AUG, is responsible for encoding methionine.

So, option (A) is correct.

Note: Because singlet or doublet codons can't adequately code for 20 amino acids, genetic coding is a triplet. The genetic code consists of 20 different triplet codon pairings. Since this is a minimum need, triplet codons can be used to encode all amino acids.