Mitosis/cell cycle Flashcards
what is included in cell cycle
- G1, S, G2, M = nterphase
- mitotic phase
why do cells divide
- growth and development
- repair and renewal
- reproduction
how long is cell cylce in humans
24hrs
explain G1
- gap
- synthesis of RNA, proteins and organelles
-decide whether should proceed to replication
explain S
= synthesis
- replication of DNA
- short phase = 5 hrs
- each cell contains 46 chromosomes, each now having 2 chromatids ready to divide
what are chromatids vs chromosomes
- chromatids if there are two joined at the centromere
- chromosomes if only one (not joined)
explain G2
- gap 2
- checking for errors
- DNA repair
- preparing for mitosis -> CELL GROWTH and protein synthesis
what is M phase
mitosis phase
- nuclear division nto two genetically identical daughter cells
- 30-45 mins
how is DNA checked - explain checkpoints
- there are checkpooints in CC that ensure cell is ok
1. G1-S transition contol, checks cell is ready for replication in S phase - size, proteins ready and damage to DNA checked
2. G2-M control = checks size, if replication is complete and if proteins are made
3. metaphase-anaphase control = check if mitosis is occuring correctly - connection to spindle fibres and distribution of chromosomes into daughter cells
What are clyclin-dependent kinases and cyclins
CDK = enzymes that activate proteins requires for cell cycle to conitnue
cyclins = protein that bind to CDK and activate
These allow cells to pass checkpoints onto next phase
apoptosis vs necrosis
ap = programmed cell death and is a normal process, affects one cell, beneficial
necrosis = premature death (swell and rupture)
- not normal, results of external factor, uncontrolled, affects many cells, destructive, causes inflammation
what is apoptosis triggered by
- apoptotic signals - e.g. hormones
- DNA damage
explain structure of chromosomes
- centormere
- small/top arm = p arm
- long/bottom arm = q arm
forms of chromosomes
- telocentric - very small p-arms
- acrocentric - shorter p arm
- submetacentric - almost equal
- metacentric = equal
what is the distance between two base pairs
- 0.34 nm
packaging of DNA
DNA molecule -> nucleosomes (hstones added) -> chromatin firbe -> loop -> heterochromatin -> chromosome
what is a karyotype
- visualisation of complete set of chromosomes in individuals
- taken in metaphase stage
- longest to smallest, sex on end
advantages and disadvantages of asexual reproduction
Ads:
- efficient
DIS:
- lack of genetic diversity
- reduced ability to adapt to new environments
how to calculate DNA length in a cell
= base pairs x 0.34
usually = 6x10^9 x 0.34
= 2m
explain prophase
- chromosomes condense
- centrosomes migrate to poles
- spindles form
- asters (ends of spindles) form
heterochromatin vs euchromatin
heterochromatin = tightly wound and condensed DNA that cannot undergo transcription
euchromatin = loosely wound
what are centrosomes
- microtubule organising centre
- each centrosome has pair of centrioles
- replicated during S phase
Explan Prometaphase hard
- fragmentation of nuclear membrane - breakdown of nuclear envelope
- centrosoms move towards opposite sides
- spind;es attach to chormatids at centsomere
Explain metaphase
- fully condensed chromosomes align along metaphase plate
- checkpoint
explain anaphase
- A = chromosomes pull towards spindle poles via centromere
- B = spindle poles move away from each other
explain telophase
- daughter chromosomes reach spindle poles
- nuclear envelop reforms
- chromosomes decondense
- spindle dissasembles
explain cytokinesis
- separation of cytoplasm
- cleavage furrow (actin along equator)
phases of Mitosis
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
- cytokinesis
