Cell Division Flashcards
G1
Synthesis:
- protiens
-new organelles like centrosomes
- cell size increases
G1 CHECKPOINT
Checks for cell size, nutrients, growth factors, and DNA damage.
S
Synthesis phase: DNA replicated via semi conservative replication, each of the 46 chromosomes is duplicated.
G2
Synthesis of molecules need for cell division.Duplicated DNAchecked for damage. cell increases in size
G2 CHECKPOINT
Checks for cell size, dna replication, and dna damage.
SPINDLE ASSEMNLY CHECKPOINT
Checks for chromosome attachment to spindle.
What carries out checkpoint checks?
Cyclins
Order the stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
PROPHASE
DNA is condensed
Sister chromatids visible.
METAPHASE
Nuclear envelope has broken down
Centrioles move to poles of the cell.
Centrioles anchor spindle fibres.
Sister chromatids line along the middle of the cell.
ANAPHASE
Spindle fibres attach to centrosomes and get shorter.
This pulls the chromatids apart.
Centrosome splits with the division of chromatids.
Chromatids now called chromasomes.
Migrate to opposite ends of the cell.
Identical copy of full set of chromosomes at either end of the cell.
Cytoplasm starts to pinch in middle.
TELOPHASE
Nuclear envelope re formscaround each set of chromosomes.
Division spindle breaks down.
Pinch now deepened and called a cleavage furrow.
Chromosomes start to dispurse like before mitosis.
CYTOKENISIS
- not part of mitisis
- part where cell actually splits.
- daughter cells will now move into G1
Cytokenis is not the same in plant cells…
- instead of the cytoplasm splitting apart, they have a cell plate that forms down the middle of the cell.
- only cells that undergoe mitosis are MERISTEM cells
- plant cells do not have centrioles.
chromatin
what constitutes chromosomes
Bivalent
A replicated homologous pair. Two replicated chromosomes, one from each parent (4 sister chromatids)
Homologous
Same length, sequence and centromere location.
Prophase 1
Chromosomes condense, and homologous chromosomes pair up to make bivalents.
Metaphase 1
Bivalents line up at a random orientation.
Anaphase 1
Spindle fibres shorten. Bivalents pulled apart, sister chromatids remain joined together.
Telophase 1
nuclear envelope reforms. cleavage furrow.
Prophase 2
Condenses, nuclear envelope breaks down.
Metaphase 2
Chromosome line up and spindle fibres attatch.
Anaphase 2
Spindle fibres shorten, chromosomes pulled apart.
Telophase 2
Chromatids dispurse again, nuclear envolope reforms.
Chiasmata/ recombination
Bivalents form, DNA gets tangled, snaps off, and rejoins. Results in a different combination of alleles.
Independant Segregation/ random assortment
Bivalent orientation is random. meaning a random assortment of chromosomes at each pole after anaphase stage. Results in a different combination of chromosomes after anaphase 2.