cell division Flashcards
cell cycle
series of events which takes place as cell grows and divides
interphase
phase of cell cycle where cell is NOT dividing (subdivided into growth and synthesis phases)
G1
rapid growth phase
- ATP production
- manufacture of new organelles and proteins
S
- DNA duplication
G2
- cell growth
- rapid ATP production
- chromosomes checked for errors and repaired
mitosis
nuclear division
checkpoint 1 (G1)
ensures cell can enter S phase
- cell size
- nutrients
- growth factors
- DNA damage
checkpoint 2 (G2)
ensure cell is ready for mitosis
- cell size
- DNA damage/ replication errors
prophase MITOSIS
- chromatin fibres condense into chromosomes which are now visible
- nucleolus disappears
- nuclear envelope disintegrates
(in animal cells centrioles migrate to opposite poles) - spindle fibres form
- spindle fibres attach to centromeres
metaphase MITOSIS
- chromosomes moved by spindle to cell equator
2. chromosomes held in place
anaphase MITOSIS
- centromeres divide
- shortening spindle fibres cause chromatids to be pulled to different poles of the cell
(characteristic V shape, as they are pulled through cytosol)
telophase MITOSIS
- nuclear envelope reforms
- nucleolus reforms
- chromosomes uncoil
- spindle disintegrates
cytokinesis
animals
- cleavage furrow forms and ingresses
plants
- cell plait laid down in the centre
prophase 1 MEIOSIS
- chromatin fibres condense into chromosomes now visible
- nuclear membrane disintegrates
- homologous chromosomes pair up in synapsis
(1 pair = 1 bivalent, 2 chromatids joined at chiasma)
- crossing over of genetic material - centrioles migrate to poles
- spindle fibres form
metaphase 1 MEIOSIS
- bivalents pulled to the centre of the cell, attached by centromeres
(independent assortment)
anaphase 1 MEIOSIS
- spindle fibres pull homologous chromosomes to poles of the cell
telophase 1 MEIOSIS
- nuclear envelope reforms
2. chromatin fibres uncoil
prophase 2 MEIOSIS
- chromatin fibres condense
- nuclear envelope disintegrates
- spindle fibres form
metaphase 2 MEIOSIS
- chromosomes line up at the centre of the cell
anaphase 2 MEIOSIS
- centromeres divide
2. chromatids pulled to poles of the cell
telophase 2 MEIOSIS
- nuclear envelope forms
- chromatin fibres uncoil
centrioles replicate - spindle fibres disintegrate
genetic variation in meiosis
- independent assortment of bivalents
- separation of bivalents
- crossing over of segments in synapsis
- haploid cells (gamete only carries 1 allele for the particular gene)
ALL produce large numbers of allele combinations
differentiation
- process by which cells specialise to take on different roles in tissues and organs
- when cells differentiate they become adapted to their specific role
stem cell
undifferentiated cell able to express all of its genes and divide by mitosis
embryonic
adult/tissue
umbilical cords
meristematic tissue
totipotent
source - embryo
pluripotent
source - bone marrow
multipotent
source - umbilical cord
pluripotent
source - tips of shoots, roots
yeast cell division
reproduce asexually by budding
- swelling of cell surface - creates a bulge
- nucleus moves into the bulge
- bulge is pinched off/ breaks off
homologous chromosomes
- 1 maternal + 1 paternal chromosome
- carry the same genes
- same/different alleles
- joined at centromere
