There are many terms pertaining to chromosomes, genes and DNA that you must get accustomed with to understand how cellular division or duplication works. Cellular duplication or division is at the crux of growth, including birth of an organism.
Difference Between Homologous Chromosomes and Sister Chromatids
The primary difference between homologous chromosomes and sister chromatids is simple enough to understand. Homologous chromosomes are similar chromosomes that are already present in the cell at the beginning of meiosis. Sister chromatids are identical in nature and they are formed in the first stage of meiosis. To fully understand the difference between homologous chromosomes and sister chromatids, one must talk about the first phase of meiosis.
Cells can divide and multiply in two ways. Known as methods of cell division or duplication, the processes are mitosis and meiosis. Meiosis is sexual division of cells and mitosis is asexual division of cells. Meiosis is a biological process that causes the division of the nucleus in a cell. Only organisms capable of sexual reproduction would have cells undergoing meiosis. Meiosis can be split into two major phases, Meiosis I and Meiosis II. The first or the original cell duplicates, the chromosomes are halved and then the two new cells formed contribute half of their chromosomes to form the new cell.
The complete process of meiosis has four stages, known as prophase I, metaphase I, anaphase I and telophase I. The first phase is the division of the nucleus of the original or first cell. Homologous chromosomes are already present in this original cell. When the division of the nucleus is completed resulting in the formation of haploid cells. Homologous chromosomes are contributed to by the mother and the father. Both contribute one chromosome each thus forming the homologous pair. Sister chromatids are formed in the prophase I or Meiosis I if you consider the larger picture. These sister chromatids are identical.
Homologous chromosomes are also relevant for mitosis. In diploid cells that have to duplicate or undergo cellular division through the asexual process of mitosis, the homologous chromosomes are existent in the original cell undergoing duplication. Homologous chromosomes are of the same shape and size, they may or may not contain the same genes and they are certainly not a duplicate version of one another. Sister chromatids are essentially a replicate or a copy of the original chromatid. Hence, the two are identical or exactly similar. Crossing over happens in homologous chromosomes, also known as homologous pairs, and not sister chromatids.
