ABSTRACT
In order to understand the basis for genetic mapping of disease, we need to consider
the events that take place duringmeiosis, the formation of sex cells, also referred to as
gametes. Sex cells (i.e. egg and sperm cells), unlike other cells in the body (referred
to as somatic cells) only carry one copy of each chromosome, either the mother’s or
father’s. Meiosis starts when a cell carrying 2 copies of each gene duplicates all of
the chromosomes in the genome. Once the chromosomes have been duplicated, the
cell divides into 2 cells with 2 copies of each chromosome. Then these 2 cells both
divide one more time, resulting in 4 cells with 1 copy of each chromosome. Each
of these 4 cells has a mix of chromosomes from the 2 parental sources so that each
chromosome is equally likely to be found in the resulting 4 cells. When 2 sex cells
fuse, the result then has a pair of chromosomes.
