Cell Division
Process that results in genetically identical daughter cells
Mitosis
Occurs in somatic cells (2 sets of chromosomes)
Meiosis
Occurs in gametes/sex cells (1 set of chromosomes)_
Binary Fission
Asexual reproduction, occurs in prokaryotes
Eukaryotic Cell Cycle
Consists of 2 main phases
1) Interphase
2) Mitotic Phase
Interphase
3 Parts of Interphase
G1: normal cell metabolism ‘resting state’
S: DNA replication, this occurs prior to the cell dividing
G2: Preparation for cell division
The time a cell spends during interphase is dependant on the cells, interphase cells are metabolically active
Mitotic Phase
2 parts of the Mitotic Phase
M: division of the nucleus, consists of 5 phases, prophase, prometaphase, metaphase, anaphase, telophase
Cytokinesis: the division of the cytoplasm
G0 Phase
Cell hibernation, do not divide
Prophase
First Step of Cell Replication
The chromosomes condense and centrosomes move to the opposite sides of the nucleus, initiating the formation of the mitotic spindle
Prometaphase
Second Step of Cell Replication
The nuclear envelope breaks down and the condensed chromosomes attach onto the mitotic spindle
Both sister chromatids of each chromosome attach to the spindle at a specialized region called the kinetochore
Metaphase
Third Step of Cell Replication
The mitotic spindle moves the condensed chromosomes to the middle of the cell
Anaphase
Fourth Step of Cell Replication
The microtubules pull the sister chromatids apart
As the microtubules contract, the chromatids are pulled into opposite sides of the cell
Telophase
Fifth and Final Step of Cell Replication
The two separate sets of chromosomes each start to form their own new nuclei
Cell splits into 2 via Cytokinesis
Cytokinesis
The split of a cell into two daughter cells
Actin filaments congregate near metaphase plate to form a ring around the inside of a cell
Pinching action separates cytoplasm into two separate cells
Cell Checkpoints
Ensures all requirements are satisfied before the continuation of the cell cycle and does not result in defective cells
Checkpoints are regulated by differing concentrations of cyclin, Cyclin-Dependant Kinase (CPK), and Maturation-Promoting Factors (MPF)
G1 Checkpoint
First Checkpoint
Cell decides whether replication is necessary, dependant on cell size, nutrients, and growth factors
G2 Checkpoint
Second Checkpoint
Ensures that DNA replication occurs properly, prevents the cell from entering mitosis when DNA is damaged
M Checkpoint
Third and last Checkpoint
Occurs during the Metaphase stage and ensures that the sister chromatids are properly attached to the spindle microtubules.
Cancer cause
Caused by the loss of cell cycle control and the uncontrolled proliferation of cells. Mutations thar result in oncogenes and defective tumour suppressor genes can lead to cancer
Oncogenes
When genes that actively promote cell division (proto-oncogenes), are not turned off at the right times, they become oncogenes and lead to cancer
Can occur in several ways, such as translocation or transportation (gene moved to a new locus under new controls), gene amplification (multiple copies of the gene) and point mutation, within the control element or in the gene
Tumour Suppression Genes
Normally inhibit cell division, when it stops working it can also lead to cancer
Common Suppressor gene is p53, when mutated leads to increased cell division