Paternal and Maternal Chromosomes
Every man has 23 sets of chromosomes.
Each set of chromosome is called homologous chromosomes because
they contain the genes coding for the same characteristics. For
example, if chromosome A and B both contain a gene that codes for
eye color, they are known as homologous chromosomes. Note that
although A and B have the same gene loci, the genes they contain
do not necessarily be identical. A could code for black eye while
B codes for blue eye. One of the homologous chromosomes comes from
the father (paternal) and their other comes from the mother
(maternal) during fertilisation.
In prophase I of meiosis, the homologous
chromosomes pair up, and the they are visibly joined at several
points (chiasmata) along their length. Each chiasma is the site of
an exchange between non-sister chromatids. The chromosome segments
break at the chiasmata and mutual exchange of segments occur. When
the segments are rejoined, the resulting two of the four
chromatids present end up with a unique and scrambled combination
of parental genes.