During meiosis, specifically in prophase I, homologous chromosomes undergo a process known as synapsis. This is where the homologous chromosomes pair up, allowing for the exchange of genetic material. Each homologous chromosome consists of two sister chromatids, resulting in a total of four chromatids when the two homologous chromosomes come together. These four chromatids can be identified and named as follows:
- Sister Chromatid 1: One of the two identical copies of the first homologous chromosome.
- Sister Chromatid 2: The second identical copy of the first homologous chromosome.
- Sister Chromatid 3: One of the two identical copies of the second homologous chromosome.
- Sister Chromatid 4: The second identical copy of the second homologous chromosome.
Each of these chromatids contains identical genetic information due to DNA replication that occurs prior to meiosis. This pairing is crucial for processes like crossing over, which increases genetic diversity in gametes. Overall, understanding these four chromatids is essential for grasping the complexities of genetic inheritance and variability.