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MODEL PAPER 10 — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYMODEL PAPER 103 Marks
Question
Observe the diagram of Genetic code and answer the following questions:
Image
i. How many codons codes for amino acids and how many do not?
ii. Explain the following giving one example of each.
a. Unambiguous and specific codon
b. Degeneration codon
c. Universal codon
d. Initiator codon
✓

Answer

i. Out of 64 codons 61 code for amino acids and rest 3 codons do not code for any amino acids. These function as stop codons.
ii. a. Unambiguous and specific codon These code for only one amino acid, thus, making the genetic code unambiguous and specific e.g. UUU.
b. Some amino acids are coded by more than one codon, so the code is degenerate, e.g. serine is coded by 6 codons.
c. The codon is nearly universal. Some exceptions to the rule are mitochondrial codon and in some protozoans, e.g. UUU.
d. Initiator codon AUG has a dual function. It codes for methionine and also acts as an initiator.

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