Explain (in one or two lines) the function of the followings:
a. Promoter b. tRNA c. Exons

Explanation

a. Promoter is a central gene that directly controls the structural genes in lac operon.
b. tRNA is also called adapter molecule. In structure, the tRNA is a compact molecule which looks like inverted L. It plays an important role in protein synthesis. It is the smallest RNA and has a triplet code which is complementary to a codon in the mRNA called anticodon. It also has an amino acid acceptor end to which it binds to amino acids.
c. The coding or expressed sequences of the DNA are called exons. The exons are interrupted by non-coding sequences called introns.