Lesson 32 - The cell cycle and mitosis Flashcards
What are the stages of cell division?
Interphase
mitosis
cytokinesis
What are the 3 stages of interphase and what happens in each of them?
G1 phase - cell growth
S phase - DNA replication
G2 phase - preparation for mitosis
What are the 4 stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens in prophase?
- Longest phase
- Chromosomes condense (shorten and thicken and become visible).
- Centrioles move to opposite ends (POLES) of the cell
- Spindle fibres start to develop (Protein microtubules radiating from each centriole and extending pole to pole)
- Nuclear envelope disintegrates & nucleolus disappears
What happens in metaphase?
- Chromosomes attach to spindle fibres by their centromeres
- They line up at right angles along the equator (middle) of the cell
What happens in anaphase?
- Stage is very fast
- Centromeres divide into 2
- Spindle fibres shorten and pull chromatids to opposite poles of the cell (centromere first)
What happens in telophase?
- Chromatids have reached the poles and are referred to as chromosomes again
- Chromosomes begin to lengthen and uncoil and lose visibility (decondense to spread out form of chromatin)
- Spindle disintegrates
- Nuclear envelope reforms and nucleolus reappears
- Nuclear division is complete
What is the importance of cell division?
- Growth: all living organisms grow (Mrs Gren) by increasing their size or their number of cells
- Repair/Replacement: no cell lasts forever/calls may get damaged, so they need to be replaced with identical cells
- Reproduction: producing gametes for reproduction
What is the definition of mitosis?
NUCLEAR division that produces two daughter nuclei that are genetically identical to the parent nuclei as well as each other
What happens in G1 phase in interphase?
Cellular components, excluding chromosomes, are duplicated
What happens in S phase in interphase?
Each of the 46 chromosomes is duplicated by the cell
What happens in G2 phase in interphase?
The cell ‘double checks’ the duplicated chromosomes for error, making any needed repairs
What are centrioles?
- Small hollow cylinders
- A centrosome = 2 centrioles (orientated at right-angles to each other)
- Form a network of fine fibres in the cytoplasm called the cytoskeleton made out of microtubules and filaments
What is the function of centrioles?
- Supports the cell’s shape
- Organise and move organelles
- During cell division the pair separate to opposite ends of the cell and form the spindle
What is the mitotic index?
The ratio of the number of cells undergoing mitosis to the total number of cells
