2.6 Cell division, cell diversity and cell differentiation Flashcards
define cytokinesis
Cytoplasmic division following nuclear division, resulting in two new daughter cells.
define interphase
phase of cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phases.
define mitosis
type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell.
explain how the cell is prepared for mitosis.
in interphase there are checkpoints which carefully order and controll the cell to prepare for mitosis.
checkpoint G1/S also called the restriction point, and the G2/M checkpoint.
The purpose of these checkpoints is to prevent uncontrolled division that would lead to tumors(cancer).
To detect and repair damage to DNA.
Becuase the molecular events that control the cell cycle happen in a specific sequence, they also ensure that:
the cycle cannot be reversed
the DNA is only duplicated once during each cell cycle.
State how prokaryotic cells undergo asexual replication.
binary fission,
Explain the events within the cell at phase M
A checkpoint chemical trigger condensation of chromatin.
Halfway through the cycle, the metaphase checkpoint ensures that the cell is ready to complete mitosis.
Cell growth stops
nuclear division consisting of stages PMAT
cytokinesis
Explain what happens at G0 phase
G0 is a resting phase triggered during early g1 at a restriction point by a check point chemical.
some cells, epithelial cells lining the gut, do not have this phase.
in this phase, cells may undergo apoptosis, differentiation.
some types of cells remain in this phase for a very long time or indefinitly.
explain what happens at the G1 phase
A g1 control point controls mechanisms ensures that the cell is ready to enter s phase and begins DNA synthesis
- cell growth and increase in size
- transcription of gene to make RNA occurs.
- organelles duplicate.
- Biosynthesis. Protein synthesis including making enzymes needed for DNA replication in s phase.
- p53 (tumor supressor) gene helps control this phase.
Explain what happens in S phase
Chromosome are unwound and the every molecule is replicated.
Housekeeping genes are replicated first.
Once the cell has entered this phase it is commited to completeing the cell cycle.
DNA replicates
once the DNA replicates the chromosomes consist of two indentical sister chromatids.
this is the phase which DNA is more subseptible to mutigenics.
Explain what happens in g2 phase
Special chemicals ensures that cell is ready for mitosis by stimulating protein that will be involved in making chromosomes condense and in formation of the spindle.
cells grow.
Explain what happens during cytokenesis
Once mitosis is complete the cell is split into two, so that each new cell contains a nucleus.
- in animal cells, the plasma membrane folds inwards and “nips in” the cytoplasm
- in plant cells, a plate forms across the equator where a cell wall forms and aswell as a plasma membrane.
explain what happens during telophase
- two sets of chromosomes
- new nuclear membranes form.
- separated chromosomes reach the poles
- a new nuclear envelope forms around each set of chromosomes
- the cell now contains two nuclei each genetically identicall to each other.
explain what happens during anaphase
Chromatids begin to be pulled apart
centromere of each pair of chromotids splits
motor proteins walk along tubulin threads pulling each sister chromatids pairs in oppersite direction.
because centromere is pulled first they form a V-shape.
Explain what happens in metaphase
- chromosomes attached to spindle equator
- spindle equator
- centromere
- tubulin threads
-The pairs of chromatids attach to the spindle threads of the equator region.
Explain events during prophase.
- Spindle forming
- nuclear envolope breaking down
- centromere
- sister chromtids
Events during stage
- indentical sister chromatids supercoils
- the nuclear envolope breaksdown
- centrioles in animal cells divides and two new daughter centrioles move to oppersite poles
- cytoskelton proteins (tublin) thread from spindle has a 3d structure is formed from cytoplasm.
Explain the importance of meosis
Sexual reproduction increase genetic variation as it combines genetic material from two individuals
for sexual reproduction to occur they haplids must fuse to create a zygote.
Define haploid
Having only one set of chromosomes represeated by the symbol ‘n’
define homologous chromosomes
matching chromosomes, containing the same genes at the same places(loci). They may contain different alleles for the some of the genes.
define meiosis
type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cells.
explain the significance of mitosis
Asexual reproduction - single cell organism like amoeba and paramecium divide by mitosis, some plants produces more individuals.
Growth - all multicellular organisms grow by producing more cells that are gentically identical.
Tissue repair- wounds heal when growth factors, secreted by platelets and macrophages and damaged cells of bloood-vessel walls stimulating proliferation of endothelial cells and smooth muscle cells to repair damaged blood vessels.
Define mitosis
Type of nuclear division that maintains the chromosome number,
each new daughter cell contains the same genetic information as the parent cell. they are also genetically identified to each other.
Define Cytokines.
Division of the cytoplasm of a cell following mitosis.
Define chromatids
replicates of chromosomes.
