WHAT ARE GENES?

     The unit of heredity is a gene. It is sequence of nucleotides that codes the amino acid sequences of polypeptides or for RNA. Beadle and Tatum proposed the one-gene –one –enzyme theory, which states that the production of a given enzyme is under states that the production of a given enzyme is under the control of a specific gene. If there is change in the control of a specific gene. If there is change in the gene, the enzyme will not be synthesized properly or will not be made at all. Scientists later on discovered that one gene is responsible for synthesis of one polypeptide i.e., one-gene-one-polypeptide”. Genes are subjected to random mutations that give rise to new alleles. An allele that is present in the most individuals in nature is considered to be “wild type”. Other alleles of the gene are called as mutant alleles. The wild type and mutant alleles. The wild type and mutant alleles reside at the same locus and for inherited according to Mendel’s laws. Many genes have multiple alleles. Multiple alleles increase the number of possible phenotypes e.g., coat color in rabbits is determined by one gene with four alleles. Any rabbit with C allele (paired with any one of the four) is dark gray, and rabbit with cc is albino (Table B.3.2).