1. When synapsis occurs a process called_____________occurs.

2. There are______definite phases of meiosis_______and meiosis.

1. When synapsis occurs, a process called "crossing over" occurs.

To understand how synapsis and crossing over work, let me explain the process of meiosis first. Meiosis is a type of cell division that occurs in sexually reproducing organisms, resulting in the production of gametes (sex cells) like sperm and eggs. Meiosis consists of two rounds of cell division, called meiosis I and meiosis II.

During meiosis I, the homologous chromosomes pair up with each other in a process called synapsis. This occurs in a specific stage known as the "zygotene" stage of prophase I. The synapsis of homologous chromosomes is vital for ensuring genetic diversity in offspring.

Now, let's talk about crossing over. Crossing over, also known as genetic recombination, is the process where sections of DNA from homologous chromosomes are exchanged with each other. It occurs during the paired state of homologous chromosomes in meiosis I, precisely at the "pachytene" stage of prophase I.

Crossing over is an essential mechanism for introducing genetic variation in offspring. It allows for the exchange of genetic material between homologous chromosomes, increasing the genetic diversity in the resulting gametes and ultimately in the offspring.

Therefore, when synapsis occurs during meiosis, the process of crossing over occurs as well. This process plays a crucial role in producing genetically diverse gametes, contributing to the genetic variation observed in populations.

2. There are two distinct phases of meiosis: meiosis I and meiosis II.

Meiosis I is the first round of meiotic cell division and consists of several stages: prophase I, metaphase I, anaphase I, and telophase I. During prophase I, synapsis occurs, and crossing over happens. Metaphase I is characterized by the alignment of homologous chromosome pairs at the equatorial plate. Anaphase I involves the separation of homologous chromosomes, while telophase I marks the completion of the first division, resulting in two haploid cells with duplicated chromosomes.

Following meiosis I, there is a brief interphase called interkinesis, which varies in duration depending on the organism.

Meiosis II, the second round of meiotic division, resembles a more typical mitotic division. It involves prophase II, metaphase II, anaphase II, and telophase II. In prophase II, the nuclear envelope disintegrates, and the spindle fibers form. During metaphase II, the chromosomes align at the equatorial plate. Anaphase II and telophase II result in the separation of sister chromatids, followed by the formation of four haploid cells, each containing one set of chromosomes.

In summary, meiosis consists of two distinct phases: meiosis I and meiosis II. Meiosis I includes the critical process of synapsis and crossing over, while meiosis II involves the separation of sister chromatids.