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3.5 explain the role of gamete formation and sexual reproduction in variability of offspring
explain the role of gamete formation and sexual reproduction in variability of offspring
- Gamete formation results in the halving of the chromosome number (n) (diploid to haploid) and sexual reproduction results in combining gametes (haploid to diploid) to produce a new diploid organism (2n). The processes involved in forming this new organism result in variability of the offspring.
- Gametes are formed during the process of meiosis. In meiosis there are two stages that lead to variability. These are:
- random segregation of individual chromosomes with treir associated genes ie, different new combinations of the original maternal and paternal chromosomes and
- the process of crossing over where the maternal and paternal chromosomes of each pairmay exchange segments of genes making new combinations of genes on the chromosomes.
- In sexual reproduction each female or male cell produces 4 sex cells (gametes) from the process of meiosis. Each of these sex cells is haploid (has half the normal chromosome number) and has a random assortment of genes from the parent. The genes (Mendel’s alleles) are separated and the sex cells have a random assortment of dominant and recessive genes. More variability is introduced depending on which sex cells are successful in fertilisation. The resulting embryo has a completely different set of genes from either of the parents.