Genes and Alleles

Meiosis does more than halve the number of chromosomes in a cell. It also introduces Genetic Variation. Genetic variation may also arise as a result of mutation. The various sources of variation help to bring about Natural Selection which has produced the vast range of species that inhabit Earth.

Gregor Mendel (1822-84) was the first person to work out the ways in which genes are Inherited. He formulated two laws which form the basis of science of Genetics. This was an amazing feat as scientists of the time had no knowledge of DNA, Genes or Chromosomes.

In 1866 Gregor Mendel suggested that the characteristics of organsims were determined by 'units' which were handed on from generation to generation. Later these units were identified as genes which were carried on and transmitted by chromosomes. A gene is the basic unit of inheritance. 

Genes consist of DNA and have three main characteristics:

• They can seperate and combine
• 
• They can mutate
• They code for the production of specific polypeptides

The Definition of a gene based on function is 'One gene being the portion of a chromosme which codes for One Polypeptide'

Alleles are alternative forms of genes occupying a similar gene-position ( or loci…