2.5 Cell Division Flashcards
Outline G1 phase
Cell grows in volume.
Outline the stages in the cell cycle
G1 phase, S phase, G2 phase, M phase, cytokinesis
Outline S phase
All nuclear DNA Is replicated.
Outline G2 phase
More growth, preparation for cell division.
Outline cytokinesis
Division of cytoplasm and cell organelles.
Outline M phase
Nuclear division, either:
-Mitosis (produces genetically identical nuclei)
or
-Meiosis (produces gametes/haploid nuclei)
Outline what a tumour is
Tumours, or cancer, are mass cells formed as a result of uncontrolled cell division. They can occur in any tissue.
Explain how tumours are formed
In a tumour, the normal repressed state of mitosis is disrupted as a proto-oncogene mutates into an oncogene (cancer causing gene). As a result, the cells begin to divide rapidly.
Outline what happens during interphase.
Protein synthesis
ATPproduction
Increase number of organelles
DNA replication
(PAID)
State 4 causes of tumours
Ionising radiation (x-rays, gamma rays), some chemicals (tobacco smoke), viral infections (HPV), inherited traits.
State the four phases of mitosis in order
Prophase
Metaphase
Anaphase
Telophase
Describe what happens during prophase
DNA (chromatin) supercoils, condensing into chromosomes. Centrosomes move to opposite ends of the cell and spindle fibres begin to form between them. Nucleolus disappears and nuclear membrane breaks down.
Describe what happens during metaphase
Spindle fibres from the two centrosomes attach to the centromeres of each chromosome. Contraction of the spindle fibres causes the chromosomes to line up seperately along the centre of the cell.
Describe what happens during anaphase
Continued contraction of spindle fibres cause the two sister chromatids to separate/divide and move to opposite poles of cell. Once separated, they become new chromosomes.
Describe what happens during telophase
Once the two sets of chromosomes arrive at the poles, the spindle fibres dissolve and a new nuclear membrane reforms around each set of chromosomes. The chromosomes decondense into chromatin. Cytokinesis occurs concurrently with telophase.
