B2.1.4 Mitosis Flashcards
Define mitosis
The division of parent cells into genetically identical daughter cells
Four stages of cell cycle
DNA replication
Movement of chromosomes
Cytokinesis
Growth of daughter cell
DNA replication
DNA molecule unzips forming two identical strands
The dna bases on each strand are exposed
Free nucleotides in nucleus line up by each strand - complementary base pairing
Forms dna base pairs
When whole strand is complete, there are two identical molecules of dna
How do chromosomes move
Line up across the centre of the cell
Two identical copies of each chromosome (formed when dna replicated) separate and move to opposite ends of the cell
Each end now contain a full set of identical chromosomes
Two new nuclei then form
Cytokinesis
Cell membrane pinches inwards to separate and enclose the two new nuclei
Then pinches off to split the original cell into two new genetically identical daughter cells
3 separate growth stages called
G
S
G2
What is gap phase 1
When the cell grows and new cell structures and proteins are made
What is the s phase
When cells replicate its dna so that when it splits during mitosis, the two new cells will have identical dna
What is gap phase 2
When cells keep growing and proteins needed for cell division are made
first stage of mitosis
Cell has two copies of its dna spread out in long strinfs
Second stage of mitosis
DNA forms x shaped chromosomes, each arm of a chromosome is an exact copy of the other
This happens before the cell dovides
What is the 3rd stage of mitosis
The chromosomes then line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
4th stage of mitosis
Membranes form around each of the sets of chromosomes.
These become nuclei of the two new cells
Last stage of mitosis
Cytoplasm divides, two new cells containing exactly the same dna as they are genetically identical to each other and the parent cell
