Genetics

• The period between cell divisions is known as interphase.
• M phase (Mitotic phase) the cell separates the copied chromosomes to form two sets and the cell divides into two new cells. This is called cytokinesis
• G₂ phase the cell checks the duplicated chromosomes and ready to divide.
• G1 phase - the cell grows.
• S phase the cell makes copies of its 3 hours chromosomes. Each chromosome now consists of two sister chromatids.
• Living cells go through a series of stages known as the cell cycle The cells grow, copy their chromosomes, and then divide to form new.cells.
• A molecule of DNA consists of a long chain of smaller subunits DNA has four different types of subunits called nucleotices
• The hereditary information of all living cells is called DNA
• Cell division is the division of one cell to airm two new cells.
• It is important for the growth and development of our body cells, which are called the somatic cells
• Mitosis is a way of making more cells that are genetically the same as the parent cell. It plays an important part in the development of an embryo.
• 1. Prophase I - the chromatin shortens and thickens. Each chromosome visible as two chromatids are commscled by a centromers
•  The exchange of 1 pieces of chromatid materials between homologs during meiosis is called crossing over (chiasmata)
• 2. Metaphase I the tetrads line up along the equator of the cell Homologs are 2 pared along the equator.
• 3. Anaphase I the homologous par of 1. chromosomes separate.
• 4. Telophase I the cytoplasm divides. It forms two cells.
• Interkinesis Interkinesis is just similar to interphase. the only difference is that chromosomes do not replicate
• 1. Prophase II in this phase, the nuclear membrane and nucleolus break apart.
• 2. Metaphase II the chromatids are still attached to the centromeres, then moves to the equator of the cell.
• 3. Anaphase II during this stage, the chromatids separate. One chromatid from each chromosome moves to one pole of the cell. The other chromatid moves to the opposite pole.
• 4. Telophase II - In this stage, the cytoplasm divides forming two cells; each with the monoploid number of chromosomes.
• Two Successive Divisions of Meiosis

  1. meiosis I
  2. Meiosis II