mitosis Flashcards
What is the cell cycle and outline its stages
Regulated cycle of division with intermediate growth periods
-Interphase
-Mitosis
-Cytokinesis
What happens during interphase
DNA is replicated and checked for errors
Protein synthesis
Mitochondria and chloroplasts grow and divide
Normal metabolic reactions occur
Three stages of interphase:
G1-the first growth phase, the proteins from which organelles are synthesised are produced and organelles replicate.The cell increases in its size
S-synthesis phase.DNAs replicated in nucleus
G2-The second growth phase,cell continues to increase its size,energy stores are increased and the duplicated dna is checked for errors
What happens in g0 and why does it occur
Where the cell moves out of the cell cycle
When it goes through differentiation-a cell becomes specialised to carry out a particular function.this can make it unable to divide,it will carry out this function indefinitely.
DNA becoming damaged-cell division may no longer be viable. It enters a state of permanent cell arrest. Most cells will do this as they only divide a set number of times
When the no of cells that goes through differentiation o r gets damaged increase in the body what could happen
Diseases could occur
What is the purpose of mitosis
Produces 2 genetically identical daughter cells for :
Growth
Cell replacement/tissue repair
Asexual reproduction
What’s the purpose of checkpoints
What does the spindle assembly checkpoint check for
What does g1 check for
What does G2 check for
Control the mechanisms of cell cycle
They Verify if the processes that each stage have been completed correctly before the cell is allowed to move onto the next phase .
Chromosome attachment to spindle
G1- cell size, nutrients,growth factors,dna damage
G2-cell size,dna replication,dna damage
What’s the duration of the cell cycle
If a cycle lasts 24 hrs
Interphase generally last 18-20 hrs as cells spend most of the time there as G1 lasts for about 10 hours
S phase lasts according to the dna that the cell contains,the rate of synthesis is fairly constant between cells and species.Usually cells will take between 5 and 6 hours to complete S phase
G2 is shorter, lasting only 3-4 hours in most cells
Mitosis takes 2 hours
Structure of chromosomes in mitosis
Chromosomes are made of two strands joined in middle by a centromere. The separated strands are chromatids , two strands on the same chromosome are called sister chromatids
Two strands-chromosomes already made a copy of itself during interphase
After mitosis chromosomes end up as one strand chromosomes in new daughter cells
What happens during early prophase and late prophase
Early- during prophase the chrosmomes becomes more distinct.
-They coil up
-shorten
-thicken
-take up stain more intensely
The centriole divides
Nucleolus becomes less prominent.
Nuclear membrane begins to break down
Late prophase-
chromosomes have becomes more distinct and seen to consist of two chromatids joined by centromere
Protein microtubules form spindle shaped structures linking the poles of the cell. Fibres forming the spindle are necessary to move chromosomes into correct positions before division.
2 Centrioles migrate to opposite poles of the cell
Spindle fibres form and attach to specific areas on the centromeres and to move the chromosomes to centre .
Nucleolus continues to shrink and disappear
Nucelear envelope disintegrates
What happens in metaphase
The Chromosomes(w two chromatids) are moved by spindle fibres to form a plane in the centre of the cell,called metaphase plate and then held in position.at metaphase checkpoint cell checks all the chrosomes are attached to the spindle before mitosis can continue
What happens in anaphase
Centromeres holding the pairs of chromatids in each chromosome divide during anaphase . Chromatids are seperated and pulled to opposite poles of the cell by shortening spindle fibres(when they contract).
The v shape of the chromatids moving towards the pole is due to….
Them being dragged by their centromeres through the liquid cystosol.
