Cell Division, Diversity and Differentiation Revision Notes
Mitosis
Interphase
-G1 (Growth 1)– Cells carry out functions: respiring, protein synthesis, photosynthesising (if plant cell)
-S Phase (Synthesis) – DNA replicated (each chromosome replicated to form 2 sister chromatids)
-G2 (Growth 2) – Cells grow and organelles replicate
Prophase
-chromosomes condense and become visible under a light microscope
-nuclear envelope breaks down
-centrioles divide into 2 and they move to opposite ends of the cell to form a spindle fibre
Metaphase
-chromosomes line up along the metaphase plate of the cell
-the spindle fibre attaches at the centromere (middle) of the chromosome
Anaphase
-replicated sister chromatids separate when the centromere splits
-spindle fibres shorten, which pull the chromatids apart to the poles of the cell
Telophase
-separated chromosomes reach the poles of the cell
-a new nuclear envelope forms around each set
-spindle fibres break down
-chromosomes uncoil and they are no longer visible under a light microscope
Cytokinesis
-cleavage furrow appears
-redistribution of the cytoplasm between the 2 identical diploid daughter cells which have been produced
Checkpoints in Mitosis
-control the cell cycle by making sure each stage has completed and there are no errors
G1 Checkpoint
-this is where the cell commits to mitosis or enters the G0 phase
G2 Checkpoint
-this ensures the cell has undergone all the necessary changes in S and G2 phase needed to proceed with mitosis
-triggers condensation of chromosomes and cell growth stops
Metaphase
-this ensures that all of the chromosomes are attached to the mitotic spindle by a kinetochore.
G0
-resting phase that many cells enter for varying lengths of time
-triggered by a chemical released during G1 and S phase Checkpoint
-cancer cells do not have a G0 phase
-nerve cells remain in G0 phase
-lymphocytes change between dividing and G0 phase
Mitosis
Interphase
-G1 (Growth 1)– Cells carry out functions: respiring, protein synthesis, photosynthesising (if plant cell)
-S Phase (Synthesis) – DNA replicated (each chromosome replicated to form 2 sister chromatids)
-G2 (Growth 2) – Cells grow and organelles replicate
Prophase
-chromosomes condense and become visible under a light microscope
-nuclear envelope breaks down
-centrioles divide into 2 and they move to opposite ends of the cell to form a spindle fibre
Metaphase
-chromosomes line up along the metaphase plate of the cell
-the spindle fibre attaches at the centromere (middle) of the chromosome
Anaphase
-replicated sister chromatids separate when the centromere splits
-spindle fibres shorten, which pull the chromatids apart to the poles of the cell
Telophase
-separated chromosomes reach the poles of the cell
-a new nuclear envelope forms around each set
-spindle fibres break down
-chromosomes uncoil and they are no longer visible under a light microscope
Cytokinesis
-cleavage furrow appears
-redistribution of the cytoplasm between the 2 identical diploid daughter cells which have been produced
Checkpoints in Mitosis
-control the cell cycle by making sure each stage has completed and there are no errors
G1 Checkpoint
-this is where the cell commits to mitosis or enters the G0 phase
G2 Checkpoint
-this ensures the cell has undergone all the necessary changes in S and G2 phase needed to proceed with mitosis
-triggers condensation of chromosomes and cell growth stops
Metaphase
-this ensures that all of the chromosomes are attached to the mitotic spindle by a kinetochore.
G0
-resting phase that many cells enter for varying lengths of time
-triggered by a chemical released during G1 and S phase Checkpoint
-cancer cells do not have a G0 phase
-nerve cells remain in G0 phase
-lymphocytes change between dividing and G0 phase
