MITOTIC CELL CYCLE Flashcards
4 functions of mitosis
- Growth.
- Asexual reproduction.
- Used in the immune system to clone B and T lymphocytes.
- Cell replacement and tissue repair.
What is interphase made up of?
Interphase~ Normal cellular function made up of G0, G1, S & G2
this is followed by mitosis which is prophase, metaphase, anaphase, telophase.
this is then followed by cytokenisis
What is G0
When the cell leaves the cell cycle due to death or differentiation. If a cell never leaves the cell cycle it has uncontrolled division (cancer).
What is G1
Cellular contents excluding the chromosomes(genetic material) are duplicated, once the cell is in G1 it must complete the rest of the cycle.
What is S
Each of the 46 chromosomes are duplicated by the cell.
What is G2
The cell “checks” the duplicated chromosomes for errors & makes repairs.
Description of Interphase
- Cell grows to its normal size and synthesises proteins and organelles (G1).
- DNA replication of the 46 chromosome to form two identical chromatids (S).
- Replicated DNA is checked for errors and ATP is produced (G2).
- Its the preparation for division.
- No visible chromosomes, only chromatin (DNA-protein complex).
- One or more nucleoli visible in each cell.
- Nuclear envelope visible.
Description of Prophase - early
DNA condenses - chromosomes become shorter and thicker (RNA and protein synthesis stops).
Description of prophase - late
- Nuclear envelope & nucleolus disappears and disintegrates into vesicles.
- Chromosomes continue to condense and appear as paired chromatids.
- The centrosomes move to opposite poles of the cell - form asters which develop into the spindle.
- Longest phase of mitosis and same amount of DNA.
Description of metaphase
- Centrosomes at poles of the cell produce spindle fibres.
- Nuclear envelope completely disintegrated.
- Chromosomes align randomly across the equator of the spindle.
- Chromosomes are attached to the spindle by centromere.
Description of anaphase
- Centromeres detach and chromatids separate.
- Spindle fibres shorten and pull chromatids towards opposite ends of the dividing cell (centromeres first).
- A complete set of chromatids migrate to opposite sides of the cell.
- Shortest phase of mitosis.
Description of telophase
- Chromatids have separated and are now called chromosomes again.
- Chromosomes start to decondense to form chromatin (RNA and protein synthesis can start again).
- Spindle fibres disintegrate and new nuclear envelopes start to form.
Description of cytokinesis in animal cells
- Division of the cytoplasm to form 2 genetically identical daughter cells from a parent cell.
- A contractile ring, made of myosin and actin filaments assembles equatorially.
- Myosin 2 uses the free energy released when ATP is hydrolysed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow.
- Continued hydrolysis causes this cleavage furrow to ingress (move inwards).
Visible through a light microscope.
Description of cytokinesis in plant cells
- Do not contain chromosomes.
- Cortical microtubules and actin filaments rearrange to form a band that encircles the cell, just below the plasma membrane.
This preprophase band gradually narrows and predicts where the new cell wall will join the mother cell wall during division. (G2) - Golgi-derived vesicles carrying cell-wall precursors associated with microtubules accumulate in the equatorial region, and fuse to form the early cell plate. (Telophase)
- Phragmoplast microtubules reform at the periphery of the early cell plate.
New Golgi-derived vesicles are recruited into this region, fuse with the edge of the cell plate, and extend it outward. (Cytokinesis). - The membrane of the extending cell plate fuses with the plasma membrane of the mother cell, completing the new cell wall. (G1)
Description of telomeres
Telomeres are found at the ends of the chromosomes and get shorter each time the cell divides until it runs out & the cell dies. The sequence in humans is TTAGGG.
