A2 Biology: Meiosis and Variation скачать в хорошем качестве

A2 Biology: Meiosis and Variation

The focus of this lecture is how meiosis leads to an increase in genetic variation, rather than the stages of meiosis which can be covered quite easily. Meiosis consists of DNA replication followed two stages of cell division (and chromosome separation) that lead to the formation of haploid gametes from diploid cells. Gametes end up with one half of each of the pairs of homologous chromosomes. But independent assortment, crossing over, mutation all act to increase the different combinations of alleles in the gametes, so that the genetic variation increases. This is further added to, when male and female gamete alleles are combined during fertilisation. It is genetic variation that ensures variation within populations so that natural selection and adaptation can occur.