In sperm cells and oocytes the chromosomes are no longer present in twofold grouped in pairs. In these cells all chromosomes are present in singularity. In the testis and in the ovary the pairs of chromosomes split in singular chromosomes and each chromosome of a pair goes by chance to a sperm cell or an oocyte. This process is called the meiosis and is illustrated below with three chromosome pairs of a male:
.png?version=1&modificationDate=1699021161727&cacheVersion=1&api=v2&width=448&height=336)
Chromosome pair 1 consists of chromosome A and B, pair 2 of C and D and pair 3 of E and F. In the meiosis the pairs the chromosome pairs split and go by chance to a sperm cell. In this way sperm cells are created with 8 (23) different combinations of chromosomes: ACE, ACF, BCE, BCF, ADE, ADF, BDE and BDF. When a species has n chromosomes the parents create 2n different sperm cells or oocytes.
Definitions
Meiosis is the process carried out in the germ cells by which gametes are formed. In diploids this involves the creation of haploid cells (sperm, oocytes) from the diploid progenitor cells
Mendelian sampling is the random sampling of parental genes caused by segregation and independent assortment of genes during germ cell formation, and by random selection of gametes in the formation of the embryo