Question

How many effective codons are there for the synthesis of twenty amino acids?

A. 64

B. 32

C. 60

D. 61 

Answer 1

Hint: The translational process involves the formation of protein through the coding sequence of RNA. Pair of three nucleotides codes for an amino acid and the amino acid chain forms the protein. 

Complete answer:

To solve this question, we have to know about the genetic code. The genetic code is formed from the stretch of three nucleotides, each of which code for specific amino acids to form a specific protein. If there is continued formation of protein, it results in the formation of a long stretch of nonsense proteins so for these we need some punctuation. There is a special codon termed as start codon that is an AUG (i.e., ATG in the corresponding DNA sequence) that starts each protein and to stop the synthesis of protein stop codons are found. There are three types of stop codon that instruct the translational machinery that is involved in the protein synthesis to stop the protein making. A stop codon is a trinucleotide sequence inside the messenger RNA that commands the halt of the protein synthesis. The genetic code defines the relation between the sequence of DNA bases that is A, T, G, and C in a gene and the protein to be translated. The cell reads the genetic sequences that are found in a group of three bases. 

So, there are a total 64 combinations of three bases possible, among which 61 specify each amino acid and the remaining three are the stop codon. The three stop codons are; UAG, UGA, and UAA.

Hence the correct answer is option (D), 61.

Note:

If there is any change or alteration in the group of three bases that code for any specific amino acid its leads to change in the polypeptide chain and the structural change in the protein leads to many disorders like cystic fibrosis that cause due to the change in the protein that maintains the movement of salt out of the body.