Pronucleus (Pl. Pronuclei)

Pronucleus is a temporary nucleus that forms in the egg and sperm after fertilization, but before their nuclear substance is completely fused. Each of the two gamete cells has its own pronucleus, and they are usually larger in size compared to normal nuclei.

When a sperm enters the egg, it begins to penetrate until it reaches the nucleus. After this, the nuclear membranes of the sperm and egg merge, and a new nucleus is formed, containing a complete set of chromosomes from the two parent cells.

However, before this, the formation of pronuclei occurs. They contain one copy of each chromosome, and in them the initial stage of DNA synthesis and preparation for nuclear division occurs. Pronuclei also contain various growth factors and other proteins that are essential for the early development of the embryo.

During embryo development, the pronuclei fuse and a new nucleus is formed, which contains a complete set of chromosomes from both parents. This occurs approximately 12-24 hours after fertilization.

Studies of pronuclei can help in understanding the processes of fertilization and the initial development of the embryo. For example, abnormalities in the development of pronuclei can lead to various genetic disorders that can cause miscarriage or the birth of a child with birth defects.

Thus, pronuclei play an important role in the early development of the embryo and are an object of interest for research in the field of reproductive medicine.

A pronucleus is the nucleus of an egg or sperm that appears after fertilization and retains its individuality until it merges with another pronucleus. This is an important stage in the development of the embryo, since the pronuclei contain genetic information from both parents and provide the beginning of a new life.

Pronuclei are larger than normal nuclei and contain large amounts of DNA and RNA. They may also contain many chromosomes, which determine the hereditary characteristics of the future organism.

After fertilization, the pronucleus begins to divide, forming two new nuclei - the first nucleus (first pronucleus) and the second nucleus (second pronucleus). The first pronucleus contains genetic information only from the mother, and the second - only from the father. These two nuclei then fuse to form one nucleus of the new embryo.

Thus, the pronucleus is an important stage in the development of the embryo and provides the beginning of a new life containing the genetic information of both parents.

**Pronuclei** are a collection of two homologous and temporarily associated genetic materials in a cell. In the nucleus of the sperm after its mitosis, a “daughter pronucleus” is observed (more precisely, diploid: there are four daughter nuclei in the cell) - this indicates that it is bivalent. But the parent nucleus has only two chromosomes. But in the cytoplasm of the cell there are still two paired chromosomes (usually one of them contains three pairs of terminal telomeres).

**There are two types of "daughter pronucleus"