Question

Match List I with List II and select the correct option.
$\begin{array}{cc}\text{List I}& \text{List II}\\ \text{A. 64 codons}(4\times 4\times 4)& \text{1. Khorana}\\ \text{B. Polycistronic}& \text{2. Eukaryotes}\\ \text{C. Monocistronic}& \text{3. George Gamow}\\ \text{D. Establishing the complete genetic code}& \text{4. Prokaryotes}\end{array}$

• A. A - 4, B - 3, C - 2, D - 1
• B. A - 3, B - 4, C - 1, D - 2
• C. A - 4, B - 3, C - 1, D - 2
• D. A - 3, B - 4, C - 2, D - 1

Answer 1

The correct option is D A - 3, B - 4, C - 2, D - 1

Cistron is a segment of DNA which codes for a polypeptide.

In prokaryotes, an mRNA formed from a cistron can code for multiple proteins. This condition is called polycistronic whereas in eukaryotes an mRNA formed from a cistron will code for one polypeptide only. This condition is called monocistronic.

Gamow stated that in order to code for 20 amino acids with just 4 bases, the code should constitute three nucleotides. Then there would be 64 triplet codes, much more than 20 amino acids.
$4\times 4\times 4=64$

Har Gobind Khorana along with Marshall Nirenberg established the complete genetic code.