D2.1 Cell Division Flashcards
(44 cards)
What is the dividing cell referred to?
Mother cell
What are the new cells referred to?
Daughter cells
Cytokinesis
The division of a cell’s cytoplasm to form two cells.
How is cytokinesis carried out in plant cells?
1) Vesicles containing pectin line up in the middle of the cell.
2) Vesicles fuse together form a middle lamella.
2) Cellulose is added on either side to form a wall for each daughter cell.
Cytokinesis in animal cells
1) Actin and myosin proteins adjacent to the cell membrane run parallel in a ring around the equator of the cell.
2) A and M exert tension to form a cleavage furrow.
3) The membrane is pulled inwards so it eventually splits the cell.
What is an example of equal cytokinesis?
A human zygote dividing to form a two-cell embryo.
What is are examples of unequal cytokinesis?
1) Oogenesis, where the small cell is a polar cell that soon dies.
2) Budding in yeast: The mother cell develops an outgrowth with little cytoplasm that then receives its own nucleus and separates.
What happens to small cells produced by unequal cytokinesis?
They can grow and survive if they receive a nucleus and another organelle that cannot be assembled from cell components.
What do u call cells without a nucleus?
Anucleate, like red blood cells (survive for approx 120 days).
Why is nuclear division important?
- So each daughter cell can receive a nucleus and genetic information.
- Growth
- Reproduction
- Repair
Why is DNA replication important before the start of meiosis and mitosis?
- The two daughter cells produced by mitosis will have the entire genome.
- Provides enough DNA for a mother cell to divide twice in meiosis.
- Provides enough DNA for recombination by the process of crossing over.
How is DNA prepared for cell division?
1) DNA is elongated to chromatin.
2) DNA is replicated.
3) The 2 DNA molecules are condensed into structures called sister chromatins.
How does DNA condensation to chromos take place?
- DNA double helix is wrapped around histone proteins.
- Resulting structures are added together.
- Supercoiling: 10,000um of DNA packed into 1ums of chromosome.
Microtubules
Narrow tubular structures assembled by tubulin proteins.
How are sister chromatids separated?
- More tubulins are added so that microtubules extend towards the cell’s equator.
- Kinetochores at the centromere remove tubulins to make microtubules pull the chromatids to the poles.
Prophase
- Chromosomes are condensing.
- Microtubules grow from centrioles to form spindle shapes.
- Spindle microtubules extend from each pole to the equator.
Metaphase
- Nuclear membrane has disintegrates.
- Chromosomes line up at the equator,
- Spindle microtubules attach to kinetochores, sister chromatids attached to separate poles.
Anaphase
- Kinetochores shorten spindle microtubules, and the identical chromosomes are pulled to opposite poles.
- Each separated sister chromatid is now a chromosome.
Telophase
- Chromosomes have reached the pole, spindle microtubules break down.
- Chromos uncoil and the cell goes through cytokinesis.
Diplois Cell
A set of 23 homologous pairs of chromosomes.
Haploid
23 chromosomes
Prophase I
Homologous chromosomes pair up, spindle microtubules form, nuclear membrane breaks down.
Metaphase I
- Chromosomes line up randomly at the equator.
- Spindle microtubules attach to a chromosome of the pair.
Anaphase I
- Each chromosome is pulled to opposite poles of the cell.
