Short segments of DNA are exchanged between homologous chromosomes during prophase I in a process called over.

The process you're referring to is called "crossing over." Here's a step-by-step explanation:

1. During the early stages of meiosis, specifically in prophase I, homologous chromosomes (pairs of chromosomes, one from each parent) come together in a process called synapsis.

2. While the homologous chromosomes are paired up, they form a structure called a tetrad, which consists of four chromatids.

3. At this point, the process of crossing over occurs. This is when segments of DNA are exchanged between the homologous chromosomes.

4. The points where the DNA is exchanged are called chiasmata. The formation of chiasmata holds the homologous chromosomes together and allows the exchange of genetic material.

5. The result of crossing over is that new combinations of genes are formed. This leads to genetic variation in the offspring.

6. After crossing over, the homologous chromosomes separate during anaphase I, and the chromatids separate during anaphase II.

7. The end result of meiosis is four haploid cells, each with a unique combination of genes due to the crossing over process.