Q.6 Describe role of genes and alleles.
Answer:
Gene
The part of DNA (sequence of nucleotides) that contains the instructions for the synthesis of a particular protein is known as a gene.
Gene Loci
DNA of each chromosome contains thousand of genes which are in pairs, one on each homologous chromosome. The locations or positions of genes on chromosomes are known as loci.
Role of Gene
Each gene determines a particular trait in an organism. Each individual carries at least one pair of genes for each trait.
Representation of gene pairs
Pairs of genes are represented by a letter or symbol. Both members of a gene pair may be the same like ‘AA’ or ‘aa’ or ‘BB’ and different in others like ‘Aa’ or ‘Bb’. It means that a gene exists in more than one alternate forms of genes.
Alleles
The alternate forms of a gene are called alleles. If an individual has ‘Aa gene pair, ‘A’ and ‘a” are the alleles of one another. Both alleles are located on the one member separately of the homologous pair.
Separation of Alleles
When chromosomes separate during meiosis, alleles also separate and each gamete gets one of the two alleles. When gametes of both parents unite, the zygote receives one allele from each parent.