Bio 1.5: Cell division

What is cell division

• The process in which parent cell divides into daughter cells.

• Different process in prokaryotes and eukaryotes

• Almost all the cells divide through either binary fission or mitosis

How does Binary fission occur?

When DNA unravels and is replicated. That replicated DNA moves to opposite ends of the cell and the cell grows and cleaves in the middle. It finally spilts into 2 daughter cells

Where does binary fission occur?

Occurs in bacteria and other prokaryotes and is quite a simple process.

How does mitosis occur?

Involves DNA replication resulting in 2 daughter cells however there are 5 phases to this process: Prophase, anaphase, metaphase, telophase and cytokinesis

Where does mitosis occur?

Occurs in eukaryotes and is a more complex process compared to binary fission.

Mitosis: Prophase

• 1st step

• When DNS has been replicated and the nuclear membrane has been broken down. Centrioles is present.

Mitosis: Metaphase

• 2nd step

• Identical DNA strands line up at the cells equator. Spindle fibres are formed from the centrioles and attached to DNA pairs at the chromosomes.

Mitosis: Anaphase

• 3rd step

  • When the spindle fibres spilt identical DNA up and drag chromosomes to opposite poles of the cell.

Mitosis: Telophase

• 4th step

• when cell cleaves at the centre and the nuclear membrane is reformed in future spilt cells

Mitosis: Cytokinesis

• 5th step however technically connected to telophase

• The moment when the parent cell splits into two daughter cells.

How many chromosomes for humans have

All humans have 46 chromosomes (23 pairs). 22 pairs are autosomal chromosomes while 1 pair are gender chromosomes

haploid cells (n)

• 1 set of chromosomes

• In humans: n=23

• Gametes (sex cells) are haploid

Diploid cells (2n)

• 2 sets of chromosomes

• In humans: 2n=46

• All somatic (body) cells

what is DNA replication

• Prior to cell division, the 46 chromosomes replicate.

• Prior to mitosis, 92 chromatids are present within the nucleus

DNA replication pairing

• Original DNA and replicated DNA form identical pairs

• This is different to homologous pairing

Daughter cells

• Identical to parent cells

• Allow new cells to have the same structure and function as former cells

• Allows for growth of an organism