MCQ
There are 64 types of codons in genetic code dictionary because:
- AThere are 64 types of tRNA's found in cell.
- BThere are 44 meaningless and 20 codons for amino acids.
- CThere are 64 amino acids for coding.
- DGenetic code is triplet.
Explanation:
The genetic code is a triplet and this triplet nature can be explained as:
There are four nitrogenous bases (Adenine, Guanine, Thymine and Cytosine) and these four bases code for 20 amino acids.
If genetic code is a doublet then a combination of two nitrogenous bases will give 4 x 4 = 16 codons, which is insufficient for 20 amino acids.
George Gamow in 1954 explained the possibility of three letter code i.e. triplet codon. This will give 4 x 4 x 4 = 64 codons, which is more than enough to code for twenty amino acids.
Hence, the genetic code is a triplet.
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| List $I$ (Interaction) | List $II$ (Species $A$ and $B$) |
| $A$. Mutualism | $I$. $+(A), 0(B)$ |
| $B$. Commensalism | $II$. $-(A), 0(B)$ |
| $C$. Amensalism | $III$. $+(A),-(B)$ |
| $D$. Parasitism | $IV$. $+(A),+(B)$ |
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