Question

Which of the following is correct regarding genetic code?
A. UUU is the initiation codon which also codes phenylalanine.
B. There are 64 triplet codons and only 20 amino acids.
C. Three random nitrogen bases specify the placement of one amino acid.
D. UAA is the nonsense codon which also codes for methionine.

Answer 1

Hint: These carry the genetic information in the form of a series of three-base sequence which translates to form proteins. Specific arrangements of the codon triplet are responsible for the formation of specific amino acids. These amino acids then form proteins.

Complete answer: A genetic code is the set of rules by which the living cell decodes the information encoded within the genetic material to form proteins. DNA and mRNA are the carriers of genetic information. Whereas, the codon is a sequence of three nucleotides which together form a unit of genetic code in the chromosomes. Codon specifically codes for a particular amino acid in a protein and are used in initiation or termination of protein synthesis. It is also called a triplet. Following are the nitrogenous bases which form the codons: Adenine, Thiamine. Guanine. Cytosine and Uracil.
On the other hand, amino acids are organic compounds of which proteins are formed. Amino acids are formed as a result of the process of translation. It contains amino and carboxyl functional groups along a side chain (R group) specific for each amino acid. The translation is the process of protein synthesis in which the sequence of a messenger RNA molecule translates into a sequence of amino acids. It occurs in three stages namely initiation, elongation and termination. There are 64 combinations of nucleotides (nitrogenous bases) in the form of codons which code for 20 amino acids.
Hence, the correct answer is option B.

Note: Generally, there is more than one codon per amino acid which is why there are more codons than the number of amino acids. Codons, thus, form the basis of cellular organisation, hence, they carry the genetic codes that are inheritable.