Q.What is linkage? How many linkage groups occur in human beings?

Two factors responsible for genetic variation are: mutation, which creates new alleles by altering the DNA sequence, and recombination during meiosis (crossing over and independent assortment), which generates new com...

Mutation creates new alleles, while meiotic recombination shuffles existing alleles into new combinations — together these are the main sources of genetic variation.

Genetic variation among individuals of a population arises mainly from two processes. (1) Mutation: spontaneous or induced changes in the nucleotide sequence of DNA (point mutations, insertions, deletions, chromosomal changes) create entirely new alleles that did not previously exist in the population, providing the ultimate raw material for variation. (2) Recombination during meiosis: crossing over between homologous chromosomes (exchange of segments between non-sister chromatids during prophase I) and independent assortment of non-homologous chromosomes at metaphase I shuffle existing alleles into new combinations in the gametes, without creating new alleles but generating novel g …