Meiosis guarantees that in a sexual life cycle, offspring will inherit one complete set of chromosomes (and their associated genes and traits) from each parent. The transmission of traits from parents to offspring is called heredity. Another important aspect of meiosis and the sexual life cycle is the role these processes play in contributing to genetic variation. Although offspring often resemble their parents, they are genetically different from both of their parents and from one another. The degree of variation may be tremendous.

In meiosis I, crossing over during prophase and independent assortment during anaphase creates sets of chromosomes with new combinations of alleles. Genetic variation is also introduced by random fertilization of the gametes produced by meiosis.

Explanation:

The pairing of homologues at the beginning of meiosis I ensures that each gamete receives one member of each pair. The pairing of homologues brings together the near-identical sequences found on each chromosome, and this sets the stage for crossing over. Following crossing over, at least two of the four chromatids become unique, unlike those of the parent. The frequency of recombination is not uniform throughout the genome. Some areas of some chromosomes have increased rates of recombination, while others have reduced rates of recombination. Recombination or crossing over occurs during prophase I. Homologous chromosomes - 1 inherited from each parent - pair along their lengths, gene by gene. Breaks occur along the chromosomes, and they rejoin, trading some of their genes. The chromosomes now have genes in a unique combination. Independent assortment is the process where the chromosomes move randomly to separate poles during meiosis. A gamete will end up with 23 chromosomes after meiosis, but independent assortment means that each gamete will have 1 of many different combinations of chromosomes. This reshuffling of genes into unique combinations increases the genetic variation Slightly different sequences in the genetic code of different individuals from the same species. This is important for species adaptation to occur in a population and explains the variation we see between siblings with the same parents.