Question

Degeneracy of genetic code was discovered by

A.McClintock
B.Khorana
C.Ochoa
D.Barnfield & Nirenberg

Answer 1

Hint: The code specifies how codons determine during protein synthesis which amino acid can be added next. A three-nucleotide codon inside a nucleic acid sequence indicates a single amino acid, with several variations.

Complete answer:
First we should know about genetic code to answer this question. The genetic code is the set of guidelines used among living cells for the translation into proteins of information contained inside genetic material. The ribosome, which connects proteinogenic amino acids in the order defined through messenger RNA, uses transfer molecules of RNA (tRNA) to hold amino acids and reads three nucleotides of mRNA at a time, is translated.
 Now, let us find the solution from the options-
- McClintock invented transposition and used it to prove that genes are capable of turning on and off physical features. To understand the repression and the expression of genetic material from a generation of maize plants to another, she created hypotheses. Thus, option A is not the correct option.
- The first scientist to synthesise oligonucleotides chemically was Khorana. This breakthrough was the first synthetic gene in the world in the 1970s; the procedure became popular in later years. Thus, option B is not the correct option.
- In 1955, while doing experiments on high energy phosphates, Ochoa produced the breakthrough for which he won a Nobel Prize. He called the enzyme which he considered to be polynucleotide phosphorylase. Thus, option C is not the correct option.
- The consistency of the genetic code, seen as the multiplicity of three combinations of codons describing an amino acid, which is the degeneracy of codons. The genetic code's degeneracy is what reasons for the presence of synonymous mutations. Barnfield & Nirenberg were the first one to identify genetic code degeneracy.

Hence, the correct answer is option (D)

Note: The structure of DNA was identified in 1953; attempts to explain how proteins are encoded began. George Gamow postulated that to encode the 20 standard amino acids required by living cells to create proteins, sets of three bases must be used, allowing a total of 64 amino acids.