please explain complete process of mitosis and meiosis?
http://www.diffen.com/difference/Meiosis_vs_Mitosis
Mitosis and meiosis are two processes involved in the division of cells, with different purposes. Mitosis is a form of cell division that leads to the production of two identical daughter cells, while meiosis is a specialized type of cell division that produces four different daughter cells, each with half the number of chromosomes as the parent cell.
1. Mitosis:
- Interphase: The cell prepares for division by growing, replicating its DNA, and producing additional organelles.
- Prophase: The nuclear membrane breaks down, and the chromatin condenses into distinct chromosomes. The centrosomes move to opposite poles of the cell, and spindle fibers begin to form.
- Metaphase: The spindle fibers align the chromosomes along the equator of the cell called the metaphase plate.
- Anaphase: The sister chromatids separate and are pulled towards opposite poles of the cell by the spindle fibers.
- Telophase: The separated chromosomes reach the poles, and new nuclear membranes form around them. The chromosomes unwind into chromatin.
- Cytokinesis: The cell splits into two daughter cells, with each cell receiving a complete set of chromosomes and organelles.
2. Meiosis:
Meiosis is composed of two rounds of cell division, called meiosis I and meiosis II. It involves the following stages:
- Interphase: The cell prepares for division by growing, replicating its DNA, and producing additional organelles.
- Meiosis I:
- Prophase I: Homologous chromosomes pair up and undergo crossing over, where genetic material is exchanged between them. The nuclear membrane disassembles, and the spindle apparatus forms.
- Metaphase I: Pairs of homologous chromosomes line up along the metaphase plate randomly.
- Anaphase I: Homologous chromosomes separate and move toward opposite poles of the cell.
- Telophase I: Two new cells form, each with only one set of chromosomes.
- Meiosis II:
- Prophase II: Nuclear membrane disassembles, and the spindle apparatus forms again.
- Metaphase II: Chromosomes align along the metaphase plate, perpendicular to the orientation in meiosis I.
- Anaphase II: Sister chromatids separate and move toward opposite poles.
- Telophase II: Four new cells are formed, each with half the number of chromosomes as the parent cell.
- Cytokinesis occurs after both rounds of meiosis, resulting in four daughter cells.
It's important to note that in meiosis, genetic variation arises due to crossing over and the random alignment of homologous chromosomes during metaphase I. This process is responsible for the diversity of traits among offspring.