The salient features of genetic code are [2023]
(A) The code is palindromic.
(B) UGA act as initiator codon.
(C) The code is unambiguous and specific.
(D) The code is nearly universal.
Choose the most appropriate answer from the options given below.
(A) and (D) only
(B) and (C) only
(A) and (B) only
(C) and (D) only
(4)
The palindromes in DNA are base pair sequences that are same when read forward (left to right) or backward (right to left) from a central axis of symmetry. Genetic code is not a palindrome. The codon which initiates the protein synthesis is mostly AUG which codes for methionine. UGA, UAG, UAA are terminator codons which do not code for any amino acids. The code is nearly universal. For example, from bacteria to human UUU would code for Phenylalanine (phe). The code is unambiguous and specific which means that one codon specifies only one amino acid and not any other.
Select the correct statements about sickle cell anaemia. [2023]
(A) There is a change in gene for beta globin.
(B) In the beta globin, there is valine in the place of lysine.
(C) It is an example of point mutation.
(D) In the normal gene U is replaced by (A)
Choose the correct answer from the options given below.
(B), (C) and (D) only
(B) and (D) only
(A), (B) and (D) only
(A) and (C) only
(4)
Sickle cell anaemia is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG. Thus, it is an example of point mutation.
Statement I: The codon ‘AUG’ codes for methionine and phenylalanine. [2021]
Statement II: ‘AAA’ and ‘AAG’ both codons code for the amino acid lysine.
In the light of the above statements, choose the correct answer from the options given below.
Statement I is incorrect but Statement II is true.
Both Statement I and Statement II are true.
Both Statement I and Statement II are false.
Statement I is correct but Statement II is false.
(1)
The codon ‘AUG’ codes for methionine only and it act as an initiator codon. The codon ‘UUU’ and ‘UUC’ code for phenylalanine. ‘AAA’ and ‘AAG’ both codons code for the amino acid lysine.
Under which of the following conditions there will be no change in the reading frame of following mRNA? [2019]
5’ AACAGCGGUGCUAUU 3’
Deletion of GGU from 7th, 8th and 9th positions
Insertion of G at 5th position
Deletion of G from 5th position
Insertion of A and G at 4th and 5th position respectively
(1)
Insertion or deletion of three or its multiple bases insert or delete one or multiple codon hence one or multiple amino acids, and reading frame remains unaltered from that point onwards.
Which of the following features of genetic code does allow bacteria to produce human insulin by recombinant DNA technology? [2019]
Genetic code is specific.
Genetic code is not ambiguous.
Genetic code is redundant.
Genetic code is nearly universal.
(4)
As genetic code is nearly universal means almost all organisms (from a virus, bacteria to a tree or human being) will have amino acids coded by same kind of codons as given in checkerboard. So, this property is utilised to produce human insulin using bacteria.
If there are 999 bases in an RNA that code for a protein with 333 amino acids, and the base at position 901 is deleted such that the length of the RNA becomes 998 bases, how many codons will be altered? [2017]
11
33
333
1
(2)
1 codon consists of 3 bases. Therefore, a deletion on 901 position will affect 33 codons.
Which one of the following is the starter codon? [2016]
UAA
UAG
AUG
UGA
(3)
Polypeptide synthesis is signalled by two initiator codons or start codons i.e., AUG (methionine codon) and rarely by GUG (valine codon).
