Question

Genes can generally be described as having two distinct parts. What are they?

Answer 1

Every gene consists of several functional components, each involved in a different facet of the process of gene expression.

There are two main functional units of a gene,the are:

(i) The promoter region - The promoter region controls when and in what tissue a gene is expressed.In the DNA of the gene's promoter region, there are specific structural elements, nucleotide sequences, that permit the gene to be expressed only in an appropriate cell.For example, the promoters of the globin gene are responsible for their expression in erythroid cells and not in brain cells.Nucleotide sequences,in the globin gene instruct an erythroid cell to transcribe globin mRNA from that gene.These structures are referred to as cis-acting elements because they reside on the same molecule of DNA as the gene.In the appropriate cell, the cis-acting elements bind protein factors that are physically responsible for transcribing the gene.

(ii) The coding region - The structure of a gene's protein is specified by the gene's coding region. The coding region contains the information that directs an erythroid cell to assemble amino acids in the proper order to make the β-globin protein.In the coding region of a gene, the linear sequence of nucleotides encodes the amino acid sequence of the protein. This genetic code is in triplet form so that every group of three nucleotides encodes a single amino acid. The 64 triplets that can be formed by 4 nucleotides exceed the 20 distinct amino acids used to make proteins. This makes the code degenerate and allows some amino acids to be encoded by several different triplets.