Question

Describe what is meant by the ‘genetic code’.

What does the Wobble effect?

What are the two ‘sites’ on the Ribosome, and what happens at each of these sites?

Answer 1

1. Genetic code refers to the information present in the form of nucleotides on DNA. It is read in triplets. One triplet refers to one codon. Anti codon is present on transfer RNA and codon is present on messenger RNA. Both of them undergo complementary base pairing to specify one amino acid during the process of translation.

2. According to wobble hypothesis, first two bases of a codon are important in determination of amino acid. The third base is a wobble and can base pair with more than one bases on anticodon. Because of wobble hypothesis, there are more than one codons for some amino acids.

List of wobble bases -

Third base on mRNA	Third base on tRNA
C	G, I
A	U, I
G	C, U
U	A, G, I

3. Ribosomes have three sites (not two). A, P and E sites are there.

A site is aminoacyl site where tRNA comes along with its amino acid which is to be added to the growing peptide chain.

P site is peptidyl site where 2 amino acids attach by peptide bond formation by peptidyl synthase enzyme.

E site is exit site from where empty tRNA after transferring its amino acid to peptide chains exits the ribosome.

If you have to write about two sites only, than write about A and P site.