Cell Division Flashcards
division of cell nucleus
mitosis
division of the cell cytoplasm
cytokinesis
genetic information is passed from one generation to
the next generation through chromosomes
- before cell division, each chromosome is duplicated
chromosomes
long thin strands made up of DNA & protein
- protein helps DNA stay together when chromosomes
form
chromatin
long thin strands made up of DNA & protein
- protein helps DNA stay together when chromosomes
form
chromatin
series of events that cells go through as they grow & divide
- cell grows -> prepares for division -> divides itself to
form 2 daughter cells each of which begins the cycle
again
Cell Cycle
period of growth
- occurs between cell divisions
- cell spends most of its life in this phase
- g1 -> s -> g2
Interphase
cell grows bigger
- synthesizes new proteins & organelles (develops)
G1 phase (gap 1 phase, growth 1 phase)
chromosomes are duplicated
- DNA synthesis takes place
S phase (synthesis phase)
organelles and molecules required for cell division are
produced
- once complete, cell is ready for M phase (Mitosis)
G2 phase (gap 2 phase, growth 2 phase)
process of nuclear division
- producing two genetically identical daughter cells with
the same number of chromosomes as their parent cell
- responsible in increase in weight & height
- responsible for healing of a wound
- occurs in body/somatic cells
- 4 phases (P, M, A, T)
MITOSIS
Stages of mitosis
prophase -> metaphase -> anaphase -> telophase
centrosome shifts to opposite poles
- nuclear membrane & nucleolus breakdown
- chromatins change until they become double-stranded
-> chromatids
- chromatids are connected by centromere
- spindle fibers become well developed
Prophase
chromatids align themselves at equator of cell, faces
opposite pole
- centromeres of chromosomes line up in the middle ->
equatorial plate
- chromatids are attached to the spindle by a structure
in the centromere called kinetochore
Metaphase
forces from the poles pull chromatids to move
- centromere spits & separate chromatids into new,
single-stranded chromosomes
- chromosomes migrate towards their respective poles
Anaphase
final stage of mitosis
- chromosomes reach opposite poles
- chromosomes uncoil
- nucleolus & nucleus membrane begin to reform
- cytoplasm divides & a new plasma membrane begin to
reform
- cytoplasm divides & a plasma membrane partitions
itself to 2
- the formation of the new plasma membrane
completely divides the cell into 2 identical daughter
cells
Telophase
nucleus divides
karyokinesis
cytoplasm divides
cytokinesis
whole proces duration
5-10 minutes (for some animal
embryos) + 20 minutes dividing bacterium
form of cell division
- leads to production of gametes
MEIOSIS
egg & sperm cells that contain half the number of
chromosomes of an adult body cell
- adult body cells/somatic cells are diploid (containing 2
set of chromosomes)
- gametes are haploid (containing only 1 set of
chromosomes)
Gametes
includes fusion of gametes (fertilization) to produce a
diploid zygote
- life cycles of sexually reproducing organisms involve
the alternation of haploid & diploid
sexual reproduction
include 2 rounds of division meiosis I and meiosis II
* meiosis I
- homologous chromosomes become closely associated
with each other -> synapsis
* crossing over
- genetic recombination between non-sister chromatids
- chiasmata (sites of crossing over)
* homologues are separated in anaphase Iinvolves 2 successive cell divisions with no replication of
genetic material between them
- results in a reduction of chromosome number from
diploid to haploid
Features of Meiosis
chromosomes began to condense
- spindle of microtubules begin to form
- DNA has been replicated
- each chromosome consist of 2 sister chromatids
attached at the centromere
- homologous chromosomes pair up & become closely
associated during synapsis
- crossing over occurs, forming chiasmata which hold
homologous chromosomes together
- Prophase I
pairs of homologous chromosomes align along the
metaphase plate
- when microtubules from opposite poles attach to
sister kinetochores of each homologue, chiasmata help
keep the pairs together & produces tension
- a kinetochore microtubule from one pole of cell
attaches to one homologue of a chromosome while a
kinetochore microtubule from the other cell pole
attaches to the other homologue of a pair
Metaphase I
kinetochore microtubules shorten & homologous pairs
are pulled apart
- a duplicated homologue goes to one pole of the cell,
while the other pole
- sister chromatids do not separate
- (in contrast to mitosis) kinetochore microtubules from
opposite poles of the cell attach to opposite sides of
one homologue’s centromere and sister chromatids
are pulled apart
Anaphase I
the separated homologues form a cluster at each pole
of the cell
- nuclear envelope reforms around each daughter cell
nucleus
- cytokinesis may occur
- resulting 2 cells have half the number of chromosomes
as the original cell
- each chromosome is still in the duplicated state &
consists of 2 sister chromatids, but sister chromatids
are not identical because crossing over has occured
Telophase I
resembles Mitosis
Meiosis II
nuclear envelopes dissolve & spindle
apparatus forms
Prophase II,
chromosomes align on metaphase plate
Metaphase II
sister chromatids are separated
Anaphase II
nuclear envelope reforms & cytokenisis
Telophase II
