Here's a breakdown:
1. Interphase: Before meiosis begins, the cell goes through interphase, just like it does before mitosis. This phase includes:
* G1 phase: The cell grows and makes proteins.
* S phase: The chromosomes are replicated. Each chromosome now consists of two identical sister chromatids attached at the centromere.
* G2 phase: The cell prepares for meiosis.
2. Meiosis I: This is the first division of meiosis and is further divided into four stages:
* Prophase I: The replicated chromosomes condense, the nuclear envelope breaks down, and homologous chromosomes pair up (synapsis) to form tetrads. Crossing over occurs between non-sister chromatids within each tetrad.
* Metaphase I: The tetrads line up at the metaphase plate (center of the cell).
* Anaphase I: Homologous chromosomes separate and are pulled to opposite poles of the cell.
* Telophase I: The cytoplasm divides, forming two daughter cells, each with half the number of chromosomes as the original cell.
So, while the first stage of meiosis itself is Prophase I, the first thing chromosomes do in the process of meiosis is replicate during interphase.
