Question

Explain the following:
(i) Genetic Code
(ii) Founder Effect

Answer 1

(i) Genetic code:

It is defined as the sequence of nitrogenous bases on mRNA or DNA which specifies the sequence of amino acids in the polypeptide chain.

Features of genetic code are-

1. The genetic code is written in a linear form with the letters of nitrogenous bases.

2. Each word of a codon consists of three letters, therefore the codon is a triplet. So, an amino acid is specified by three nitrogenous bases in RNA or DNA.

3. The genetic code is non-ambiguous and specific as each codon codes for one amino acid only.

4. The genetic code is degenerate because each amino acid may be specified by more than one codons.

5. AUG codes for methionine and is also called as the start codon.

6. There are three stop codons UGA, UAA and UAG.

7. The code is universal with some exceptions

(ii) Founder effect:

Sometimes, one or a few individuals disperse and become the founder of a new and isolated population at some distance from the place of their origin. These newly formed individuals may not have all the alleles present in the original population from which they were formed. Thus, some alleles are lost from the new population and others may get changed in frequency. This is called Founder effect. Founder effect has been important particularly for the evolution of organisms on distant oceanic islands like Hawaiian islands and the Galapagos islands visited by the Darwin. Most of the organisms in such areas probably derived from initial founders.