Cell Cycle & Division
- Know that the cell cycle is a regulated process in which cells divide into two identical daughter cells, and that this process consists of three main stages: interphase, mitosis and cytokinesis
- Understand what happens to genetic material during the cell cycle, including the stages of mitosis
- Understand how mitosis contributes to growth, repair and asexual reproduction.
- Understand how meiosis results in haploid gametes including the stages of meiosis
- Understand that meiosis results in genetic variation through recombination of alleles, including independent assortment and crossing over.
- Understand what chromosome mutations are,as illustrated by translocations
- Understand how non-disjunction can lead to polysomy, including Down's syndrome, and monosomy, including Turner's syndrome
The cell cycle
Interphase – a period of non-division when the cells increase in mass and size, carry out normal activities and replicate DNA
- Gap 1 = The cell assimilates material, grows and develops
- S = The chromosomes replicate and become double stranded chromatids
- Gap 2 = The time that the organelles and other material is synthesised
Cytokinesis = When the new cells separate
The cell cycle is controlled by a number of checkpoints where the cycle moves into another phase. The chemicals are called cyclins and are attached to enzymes are called cyclin dependent kinases (CDKs). These form phosphorylates which bring about the next stage. For example condensing the chromosomes.
- Prophase = The chromosomes coil up and become visible, chromosomes are two daughter chromatids and a centromere, the nucleolus begins to break down
- Metaphase = The centrioles have moved to opposite poles of the cell and the chromosomes line up on a vertical equator called the metaphase plate
- Anaphase = The centromeres split and the sister chromatids are pulled to opposite sides
- Telophase = Spindle fibres break down and nuclear envelopes form and the chromosomes unravel
- Cytokinesis = The two cells split with actin causing a furrow in animal cells whereas in plant cells vesicles from the golgi apparatus at which point, they fuse together and form a wall