Cell Division (1.6) Flashcards
What are the two types of cell division?
Mitosis: The division of the nucleus into two genetically identical daughter nuclei. Occurs in all cells.Miosis: Cell division for the production of gametes (sex cells). Occurs in the ovaries and testes.
The Cell Cycle
The series of events that take place in a cell leading to its division and replication. Includes mitosis and cell growth.
What stage precedes mitosis?
Interphase - DNA is present as uncondensed chromatin in a nucleus. Centrosomes and other organelles are duplicated.
First stage of mitosis
Prophase - DNA supercoils and condenses into chromosomes. Chromosomes are made up of genetically identical sister chromatids joined at a centromere. The nuclear membrane breaks down and dissolves.
Second stage of Mitosis
Metaphase - Microtubule spindle fibres from the centrosomes connect to the centromere of each chromosome causing the chromosomes to align along the centre of the cell.
Third stage of Mitosis
Anaphase - The chromosomes segregate, pulling the chromatids apart. Move to opposite poles of the cell.
Last stage of Mitosis
Telophase - Spindle fibres dissolve. Chromosomes decondense, nuclear membranes reform. Cytokinesis occurs, splitting the cell into two nuclei.
Stage after Mitosis
Cytokinesis - Division of the cytoplasm. The cell splits in two.
Cytokinesis differences in plant and animal cells
Animal cells don’t have a cell wall so in cytokinesis a cleavage furrow is formed instead of a cell plate.
Mitotic Index
Mitotic Index = number of cells in mitosis/total number of cells x 100
Stages of the Cell Cycle
G1 - Period of cell growth. Interphase begins. S - Period where the DNA is replicated (Interphase)G2 - Period after DNA has been replicated. (End of Interphase). Mitosis - Prophase, Metaphase, Anaphase, Telophase. Nuclear division.Cytokinesis - Cytoplasm divides, forming two separate cells.
What are Cyclins?
Cyclins are chemicals that signal the beginning and end of different stages in the cell cycle. They do this by undergoing periods of chemical synthesis and by activating cyclin-dependent kinases (CDKs) which control cell processes by phosphorylation.
Metastatic cancer
Where cancerous cells spread into other surrounding tissues and travel to other parts of the body, producing new tumours.
What is a tumour?
A tumour is a group of cells that has formed as a result of uncontrolled cell division and growth.
Oncogenes
Oncogenes code for proteins that promote cell growth and the cell cycle. When oncogenes mutate they become cancer causing as they accelerate cell division.