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.

 

Relating Topics
- Dominant and Recessive Alleles
- Meiosis