cell division Flashcards
cell division
nuclear division followed by cytoplasmic division
another name for nuclear division
karyokinesis
another name for cytoplasmic division
cytokineses
diploid cells have 2 copies of every chromosome forming…
homologous chromosomes
how many chromosomes do humans have
46
(23 homologous pairs)
animal cells have cellular structures called
centrosomes
each centrosome contains a pair of
centrioles
centrioles produce
spindle fibers that will separate sister chromatids during anaphase
the cell cycle is divided into
interphase (G1, S, G2)
mitotic phase (mitosis + cytokinesis)
interphase
begins after mitosis and cytokinesis are complete
(when cells are replicated and physically separated
G1
cell increases in size
G1 checkpoint ensures everything is ready for DNA synthesis
most cell growth in volume occurs here
S
DNA synthesis
second molecule of DNA replicated from the first creating sister chromatids
when is DNA replicated
S phase
NOT mitosis
G2
rapid cell growth continues to occur
preparation of genetic material for cellular division
cell replicates organelles
G0
inactive state of cells not actively growing or dividing
what cells are examples of G0 (2)
nerve cells
cardiac cells
surface area to vol ratio
SMALL
cellular exchange is hard
leads to cell death or cell division to increase surface area
Genome to volume ratio
SMALL
as the ratio decreases the cell exceeds the ability of its genome to produce proteins needed to regulate the cell
spindle apparatus forms when
during prophase
what are crucial to cell division during mitotic phase
microtubules
mitotic spindle
what do anti-tumor drugs act on in cancers?
act as microtubule inhibitors
the drugs stabilize microtubules preventing chromosome and chromatid separation and causing cell cycle arrest (no cell division)
when does a virus impact the mitotic spindle
impacts the spindle most affects a cell during mitotic phase
each sister chromatid has a
kinetochore
where microtubules attach - not chromosomes directly
MITOSIS
prophase - chromosome and chromatids
46 chromosomes
92 chromatids
MITOSIS
prophase
nucleus disassembles
nucleolus disappears
chromatin condenses into chromosomes
MITOSIS
metaphase - chromosomes + chromatids
46 chromosomes
92 chromatids
MITOSIS
metaphase
chromosomes line up
each metaphase chromosome consists of 2 attached sister chromatids
each chromatid is complete with a centromere and attached kinetochore
MITOSIS
Anaphase - chromosomes + chromatids
92 chromosomes
92 chromatids
MITOSIS
Anaphase
microtubules shorten and each chromosome is pulled apart into 2 separate chromatids (once physically separated, each chromatid is considered a chromosome so the chromosome # has doubled)
chromosomes pulled to opposite poles
each pole has a complete set of chromosomes
disjunction
chromosomes pulled to opposite pole
MITOSIS
telophase + cytokinesis - chromosomes + chromatids
92 chromosomes
92 chromatids
MITOSIS
telophase + cytokinesis
nuclear envelope re-forms
chromosomes decondense back into chromatin and nucleoli reappear
after cytokinesis how many chromosomes and chromatids in each cell
46 chromosomes
46 chromatids
meiosis produces (from 1 diploid parent cell)
4 non-identical haploid daughter cells
meiosis I
homologous chromosomes separate
meiosis II
sister chromatids separate
Prophase I
chromosomes + chromatids
46 chromosomes
92 chromatids
prophase I
- spindles form and nuclear envelope breaks down
- chromosomes pair up lengthwise forming tetrads which need to form for crossing over to occur
- pairs are physically linked through chiasmata
- microtubules attach to chromosomes at kinetochores and move them towards metaphase plate
synapsis
chromosomes pair up lengthwise in prophase I
where does crossover occur
chiasmata
metaphase I
chromosomes + chromatids
46 chromosomes
92 chromatids
metaphase I
- homologous chromosomes are arranged at the metaphase plate
- independent assortment of chromosomes occurs because the arrangement of homologous chromosomes is random
anaphase I
chromosomes + chromatids
46 chromosomes
92 chromatids
anaphase I
homologous chromosomes separate and spindle apparatus guides the chromosomes to opposite poles
telophase I + cytokinesis
chromosomes + chromatids
46 chromosomes
92 chromatids
telophase I + cytokinesis
- homologous chromosomes are separated from each other to each end of the cell
- cytokinesis
cytokinesis I results in how many daughter cells
2 haploid daughter cells
each contain 1 chromosomes from every homologous pair
prophase II
chromosomes + chromatids
23 chromosomes
46 chromatids
prophase II
spindle apparatus forms and microtubules move chromosomes towards metaphase plate
metaphase II
chromosomes + chromatids
23 chromosomes
46 chromatids
metaphase II
- sister chromatids are no longer genetically identical due to crossing over
- chromosomes lined up at metaphase plate
anaphase II
chromosomes + chromatids
46 chromosomes
46 chromatids
anaphase II
- chromatids separate moving towards opposite ends
- separated chromatids are now chromosomes
telophase II + cytokinesis
chromosomes + chromatids
46 chromosomes
46 chromatids
telophase II + cytokinesis
- nuclei formation and decondensing of chromosomes
- cytokinesis
cytokinesis II results in how many daughter cell
4 genetically distinct daughter cells in total
3 sources of genetic variation
crossing over
independent assortment
random joining of gametes (which sperm fertilizes the egg)
crossing over
non-sister chromatids of 2 homologous chromosomes exchanging genetic material
when does crossing over occur
prophase I
independent assortment
random orientation of homologous chromosomes allows for the production of gametes with many different assortments of alleles
when does independent assortment occur
metaphase I
are genes closer together more or less likely to be inherited together
more likely
known as genetic linkage
genetic linkage
genes that are physically closer together are less likely to be separated during crossing over
chromosome number for meiosis
reduced by half
chromosome number for mitosis
remains the same
daughter cells produced by meiosis
4 haploid cells
daughter cells produced by mitosis
2 diploid cells
genetics for meiosis
different
genetics for mitosis
identical
rounds of cell division for meiosis
2
rounds of cell division for mitosis
1
division of genetic information for meiosis
sister chromatids separate at anaphase II
homologous chromosomes separate at anaphase I
division of genetic information for mitosis
sister chromatids separate during anaphase