D.2.1 - Cell and nuclear division

Mitosis

Cell divides into two genetically identical cells, used for growth and repair within an organism

Meiosis

Sex cells divide twice to create four new cells. Each of the four have exceptional characteristics making them unique from other cells and from one another

What are the exceptional characteristics?

• Each sex cell only contains half the genetic information from the parent cell

• Each cell has different combination of hereditary information from the parent cell

Why do prokaryotes need cell division?

In order to maintain the population 

Binary fission

Prokaryotic cell division; DNA is copied, daughter chromosomes attach to different regions of the plasma membrane, cell divides into two identical daughter cells.

Cytokinesis in animal vs. plant cells

Animal: fluid membrane pinches inward (cleavage furrows)

Plant: form cell plates as membrane is rigid (cell wall)

Unequal cytokinesis exp.

• Oogenesis (production of egg cells): four cells are prodcued, three of them donate their cytoplasm and organelles to the fourth so it can have enough resources to become a zygote when fertilised. 

• Yeast cells: “budding” involves the creation of a smaller cell from the parent cell following nuclear division

Meiosis genetic variety

Because each daughter cell in a gamete has a differnt combination of hereditary characteristics, the genetics of an individual are so rare. Additionally, it is extremely rare for sperm cells from the same male to have the same genetic profile.