Cell division 2 Flashcards
What two processes make up the M-phase?
Mitosis and Cytokinesis.
5 phases which make up mitosis?
Prophase, prometaphase, metaphase, anaphase and telophase.
Events of prophase?
Nuclear membrane breaks down and starts to fragments.
DNA and associated proteins within a cell start to coil up and condense.
Centrosome in animal cells (MTOC) organise microtubule fibres in the cytoskeleton.
When does the centrosomes duplicate?
S-phase.
What mediates Microtubule growth?
GTP-bound tubulin dimers to plus end of microtubule fibres.
What mediates microtubule shrinkage?
Hydrolysis of GTP to produce GDP-bound tubulin dimer - these dissociate from plus end of microtubule fibres.
Events of prometaphase?
Nuclear membrane fully breaks down.
Microtubule reorganise into mitotic spindle and attach to chromosomal centromeres at regions know as kinetochores.
Where do mitotic spindles attach too on chromosomes?
Kinetochores.
Events of Metaphase?
Replicated chromosomes line up along the equator of the dividing cell (metaphase plate).
Role of spindle assembly checkpoint?
Cells arrest in metaphase until all chromosomes are attached to mitotic spindle correctly (bipolar fashion to create equal tension).
Events of Anaphase?
The sister chromatids synchronously separate to form two daughter chromosomes; each is pulled towards opposing spindle poles (driven by microtubule dynamics).
Events of the telophase?
Set of daughter chromosomes at each pole of the cell.
Nuclear envelope begins to develop at each pole of the cell.
Contractile ring starts to contract at point where cytokinesis will occur.
Events of cytokinesis in animal cell.
Complete nuclear envelop surrounds decondensing chromosomes.
Contractile ring creates cleavage furrow.
Re-formation of interphase array of microtubules nucleated by centrosome.
Events of cytokinesis in plant cell.
Vesicles from Golgi bring cell wall material to division point.
Cell plate grows to create to separate cells.
Which eukaryotic cells divide asymmetrically by budding?
Hydra (water plant) and saccharomyces cerevisiae.
What are offspring in relation to their parent cell from mitosis?
Clones
What are offspring in relation to their parent cell from meiosis?
Genetically unique.
Is meiosis I an addition or reduction division?
Reduction.
Halves the number of chromosomes within the resulting daughter cell.
How is genetic variation increased in meiosis?
Recombination between non-homologous sister chromatids (crossing over) occurs.
Independent assortment of chromosomes in metaphase I.
Events of prophase I ?
Similarly nuclear envelope breaks down, formation of microtubule spindle and chromatin condensation occurs.
Each homologous pair of duplicated chromosomes align closely together (synapsis).
This homologous pairs are initially tightly together along entire length by a scaffold protein called synaptonemal complex.
During this phase crossing over occurs.
What is the section called when non-sister chromatids cross over and form bridge?
Chiasma.
What is the tight pairing of duplicated chromosomes in prophase I called?
Synapsis
What’s the scaffold protein which holds together homologous pairs called?
Synaptonemal complex.
Metaphase I events?
Homologous chromosome pairs are aligned at the metaphase plate by spindle microtubules.
Kinetochores assemble on one side (external) of each chromatid.
Independent assortment occurs, further increasing genetic diversity in daughter cells.
Anaphase I, Telophase I and Cytokinesis?
Homologous chromosomes pulled away from each other.
Telophase I and cytokinesis similar to to mitosis.
Is meiosis II similar to mitosis or not?
Yes, they are practically the same.
Meiosis in human males?
Prophase I last about a week with the whole miotic cycle taking a month.
4 sperm cells produced from each primary spermatocyte.
Meiosis in human females?
Prophase begins before birth but then arrest and continues post-puberty during monthly ovarian cycle.
Only one ovum is produced from each primary oocyte.
What can result due to an error in chromosomal segregation?
Failure to correctly separate pairs is referred to as non-disjunction.
Can result too many or too few chromosomes and therefore medical disorders.
