Chromosome formation and nuclear division

Chromosomes are composed of DNA and proteins and carry genetic information.
A single piece of DNA together with associated proteins is called a chromatid.
Prior to cell division, the DNA in a cell is copied, creating two identical chromatids.
These identical chromatids are held together at a point called the centromere, forming a complete chromosome.
Mitosis and meiosis are the two types of nuclear division that involve the separation of these chromatids.

Mitosis involves a single nuclear division and produces two daughter cells.
These daughter cells are genetically identical to the parent cell, each containing the same number of chromosomes.
Mitosis goes through a series of phases: prophase, metaphase, anaphase, and telophase.
Mitosis is a continuous process but dividing it into these distinct phases helps with understanding and study.
This process is important in growth, repair, and asexual reproduction.

Meiosis involves two rounds of nuclear division, resulting in the production of four daughter cells.
Each of these four daughter cells has half the number of chromosomes of the parent cell. In humans, this would be 23 chromosomes.
Because the chromosome number is halved, meiosis is necessary for sexual reproduction, as the fusion of male and female cells (each having half the full complement of chromosomes) creates a cell with the full number of chromosomes.
Meiosis also increases genetic diversity due to the shuffling of genetic material during the process.
Crossing over in the early stages of meiosis contributes to this increased genetic diversity.