Cell Division Flashcards
what is the cell cycle and its stages
regulated cycle of division and intermediate growth periods
interphase
mitosis/meiosis
cytokinesis
outline what happens during interphase
G1-synthesises proteins for replication and cell size doubles
S-DNA replicates
G2- organelles divide
what is the purpose of mitosis
produce two genetically identical daughter cells
growth
cell replacement
asexual reproduction
name the stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
outline what happens during prophase
chromosomes condense
centrioles move to opposite poles of cells and mitotic spindle fibres form nuclear envelope and nucleolus break down-chromosomes free in cytoplasm
outline what happens during metaphase
sister chromatids line up at equator attached to spindle fibres by centromeres
outline what happens during anaphase
spindle fibres contract-centromeres divide
sister chromatids separate into 2 distinct chromosomes and pulled to opposite ends of cell
spindle fibres break down
what happens during telophase
chromosomes decondense
new nuclear envelope forms around each set of chromosomes
2 new nuclei
what happens during cytokinesis
cell membrane cleavage furrow forms
contractile division of cytoplasm
how is cell cycle regulated
checkpoints ensure damage detected and do not progress
what happens at G1 checkpoint
checks for DNA damage
what happens at G2 checkpoint
checks chromosome replication
what happens at metaphase checkpoint
cell checks sister chromatids have attached to spindle correctly
what is meiosis
produces four genetically different haploid cells
what happens during meiosis 1
homologous chromosomes pair to form bivalent
crossing over occurs at chiasmata
cell divides into two
homologous chromosomes separate randomly
what are homologous chromosomes
pair of chromosomes with genes at same loci
1 maternal and 1 paternal
what happens during meiosis 2
independent segregation of sister chromatids
each cell divides again forming 4 haploid cells
how does meiosis produce genetic variation
crossing over during meiosis 1
independent assortment
how do cells become specialised
some genes expressed while others silenced due to cell differentiation
cells produce proteins that determine their structure and function
what is a transcription factor
a protein that controls transcription of genes so only certain parts of DNA expressed
how do transcription factors work
move from cytoplasm to nucleus
bind to promoter region
make it easier or more difficult for RNA polymerase to bind to gene
increases or decreases rate of transcription
what is a stem cell
undifferentiated cells that can divide indefinitely and turn into other specific types of cell
name and define the four types of stem cell
totipotent-can develop into any cell type
pluripotent-can develop into any cell type (not placenta or embryo)
multipotent-can develop into a few types of cell
unipotent-can develop into any type of cell
suggest some uses of stem cells
repair damaged tissue
drug testing
treating neurological diseases
describe the 2 groups of specialised cells in blood
erythrocytes-biconcave, no nucleus, lots of haemoglobin to carry oxygen
leucocytes-neutrophils to engulf foreign material
how do specialised cells form in blood
multipotent stem cells in bone marrow differentiate into:
erythrocytes
leucocytes
describe the structure of squamous epithelial cells
single smooth layer of squamous cells
thin and flat with round nucleus
fixed in place by basement membrane
describe the structure of ciliated epithelial cells
column shaped with surface projections called cilia
describe the structure and function of palisade cells
absorb light energy for photosynthesis
contain many chloroplasts
describe the structure and function of guard cells
form stoma
when turgid stoma opens
when flacid stoma closes
walls thickened by spirals of cellulose
describe the structure and function of root hair cells
absorb water and low concentration materials from soil
hair like projections increase surface area for osmosis
many mitochondria produce ATP for active transport
what are meristems
totipotent undifferentiated plant cells
describe the structure of phloem tissue
sieve tube elements-form tube to transport sucrose
companion cells-involved in ATP production for active loading of sucrose into sieve tubes
plasmodesmata-gaps between cell walls where cytoplasm links
