Mitosis Flashcards
1
Q
Cell division consists of 2 stages, namely:
A
- Nuclear division / karyokinesis
- Cytoplasmic division / cytokinesis
CELL DIVISION = NUCLEAR + CYTOPLASMIC DIVISION
2
Q
Definition: Cell Division
A
- formation of 2 or more daughter cells from a single mother cell
- nucleus divides first before cytoplasm; formation of plasma membrane between daughter nuclei
3
Q
Main events of Interphase
A
1) G1 (intensive cellular synthesis)
2) S (DNA replication)
3) G2 (further cellular synthesis)
INTERPHASE - LONGEST PHASE OF CELL CYCLE
4
Q
Main events of Mitotic phase
A
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
5
Q
Interphase
A) G1 PHASE
A
- increase in cytoplasm for cell growth
- ribosomes synthesised; nucleolus transcribes and assembles ribosomal materials like rRNA, nucleus transcribes DNA into mRNA for translation into ribosomal proteins
- at ribosomes, proteins synthesised (translation) & new organelles formed
- chromosomes uncondensed (chromatin)
6
Q
Interphase
B) S phase
A
- DNA replication occurs; histones synthesised
- DNA content doubles
- each chromosome consists of 2 identical DNA molecules in uncondensed form
7
Q
Interphase
C) G2
A
- further cellular synthesis; mitochondria synthesise ATP which will be hydrolysed to provide energy for nuclear division
- (ANIMALS ONLY) centrioles replicate and form 2 centrosomes; asters develop
8
Q
Mitosis
A) PROPHASE
A
- each chromatin thread and its copy produced in S phase shorten and condense by spiralisation
- become visible as chromosomes; 2 sister chromatids joined at centromere
- nuclear envelope disintegrates; reabsorbed by ER
- transcription ceases as chromosomes are condensed
- centrioles migrate to opposite poles; spindle apparatus forms
9
Q
Mitosis
B1) PROMETAPHASE
A
- a kinetochore attaches to each of the sister chromatids
- bundles of microtubules that form spindle fibres extend from each of the poles to the equator of cell; attach to kinetochores (KINETOCHORE MICROTUBULES)
10
Q
Mitosis
B2) METAPHASE
A
- spindle fibres make chromosomes align along equator
11
Q
Mitosis
C) ANAPHASE
A
- centromeres divide into two; sister chromatids of each chromosome separate and move to opposite poles of cell; considered as daughter chromosomes
- kinetochores pulled towards poles as kinetochore microtubules shorten
- cell elongates as poles move apart when non-kinetochore microtubules slide past one another
12
Q
Mitosis
D) TELOPHASE
A
- chromosomes uncoil to form chromatin and allow gene expression; nuclear envelope reforms
- spindle fibres disintegrate into tubulin monomers that make cytoskeleton of daughter cells
13
Q
Cytokinesis in ANIMALS
A
- plasma membrane invaginates towards region where equator was located by means of a constricting belt of actin filaments
- plasma membranes at cleavage furrow eventually join up and separate daughter cells
14
Q
Cytokinesis in PLANTS
A
- GA produceds small fluid-filled vesicles that first appear in the centre and are guided by microtubules
- vesicle contents form new cell walls; membranes form new plasma membranes
- vesicles fuse to form cell plate
