Question

Genetic code was discovered by frameshift mutation by
(a)Crick
(b)Watson
(c)Franklin
(d)Khorana

Answer 1

Mutations are defined as any change in the genetic code of the cell. It can be a change in the nucleotide sequence causing a change in the gene expression or it can be chromosomal change such as gene deletion or inversion. It can also be a change in the number of chromosomes known as aneuploidy.

Complete answer:
Genetic code was discovered by frameshift mutation by Francis Crick. Frameshift mutation occurs when due to a single change in nucleotide when can be insertion or deletion, the entire frame of reading the codon gets shifted, thus resulting in the production of completely different amino acid chains. This is because codons are always read in a set of three. Let us understand the process of frameshift mutation with the help of an example.
Consider there is a gene sequence
CAT SAT MAT HAT
Now if there is an insertion of a nucleotide ‘R’ after CAT will result in the following gene sequence
CAT RSA TMA THA T
We can see that all the codons after CAT have changed and thus will produce different amino acids or no amino acids.
Additional information:
Let us look at the other types of mutations seen.
Substitution: This mutation is also known as point mutation as the change occurs in a single base pair of DNA which appears like a point on the genome. A classic example of this mutation is sickle cell anemia in which the change in one base causes the production of valine instead of glutamic acid.
Trisomy of chromosomes: In such cases, there is an extra chromosome available other than the 2 homologous chromosomes. This is seen in Down’s syndrome where there are 3 copies of the 21st chromosome and in Klinefelter’s syndrome where there are 2 X chromosomes and 1 Y chromosome.
Monosomy of chromosomes: This is seen in cases like Turner’s syndrome where only one X chromosome is present.
So, the correct option is ‘Crick’.

Note: -Watson along with Crick gave the double-helical structure of DNA.
-The data from the diffraction experiments conducted by Rosalind Franklin was used to propose the model of DNA.
-Har Gobind Khorana showed the order of nucleotides present in nucleic acids.