Somatic Cell

Somatic cells is any cell of the body except sperm and egg cells. Somatic cells contain two sets of chromosome, which are found in pairs. One chromosome of each pair, a homologous pair, comes from each of the organism’s two parents. A homologous pair has similar size and appearance, except for the sex chromosome. The two chromosomes in a homologous pair are called homologs. Human have a total of 46 chromosomes, 23 comes from the mother and 23 from the father. Only 22 of them are homologous pairs. The 23rd twenty third pair, the sex chromosome (X and Y), is not truly homologous because of its size and types of genes difference in type of genes.

Two homologous chromosomes together one on top of the other. Different parts are highlighted and labeled. In the center of the chromosome the centromere and the kinetochore are shown. Both chromatids are labelled as sister chromatids. The junction between both chromosomes is referred to as synaptonemal complex.

Figure 1. Homologous chromosomes.

Non-sister chromatids are any two chromatids in a pair of homologous chromosomes that are not sister chromatids –in other words, one maternal and one paternal chromatid.