cell division Flashcards
uses of cell division
unicelular organisms: reproduction
multicel. org.:
growth, repair, reproduction
how many and what type of chromosomes do prokaryotes have
1
circular
what’s the name of cell division done by prokaryotes
explain process
(bacteria+archea) do binary fission (2 exact copies of one)
- dna replicases and cell wall grows
- DNA gets pulled apart and cell separates
what 2 types of cell division do eukaryotes do + explain their use
Mitosis: dividing somatic (not sex) cell
ex: growing, repairing cuts, replace old cells
Meiosis: division of germ (sex) cells-> it produces gametes that are different from the parents and the siblings
ex:eggs/sperm production
the phases of mitotic cell cycle
interphase mitosis (m phase)
explain interphase
(90% of the time its interphase) G1: cell growth + maintenance towards end is restriction point: have to continue and replicate DNA/divide because surface area/volume is unbalanced S phase (synthesis):dna replication (1 chromosome->2 chromatids) G2:cell grows + prep for mitosis (*2 centrosomes, etc)
stages of M phase (mitosis)
prophase prometaphase metaphase anaphase telophase
what is cytokinesis and when can it happen
division of cytoplasms
can happen after mitosis, after nuclear division
how is chromatin made
DNA wound around histone protein this is called a nucleosome
what is a eukaryotic chromosome
a strand of chromatin
tightly wrapped
describe s phase
helix unwinds and complementary base pairing is done with each strand
what are sister chromatids
when is it there
its the 1 chromosome that is now 2 identical strands held together at centromere
it is there as soon as mitosis starts also there but looser in s phase and not visible as an x
everything about centrosomes
what?
what do they do and when?
made of 2 centrioles at 90º angles
at G2-M they move to opposite ends of cell
cause formation microtubules which leads to spindle structure (like claws to drag one chromosome to one side and one to the other (look it up))
prophase
- chromosomes condense ( x (paired chromatids) visible)
- kinetochore (ring of protein forms in centromere area of each chromosome )
what are the types of microtubules in the spindle
- polar microtubules: spindle sturcture/ track
- kinetochore microtubule: connects to kinetochore of chromosome and pulls the sisters away.
prometaphase
nuclear envelope and nucleus disappear
chromosomes slowly are pushed to middle of the cell
kinetochore microtubule approach and attach them to the poles
metaphase
chromosomes are in middle of cell (called equatorial plate)
at end of this phase centromeres (holding chromatid pairs together) seperate
anaphase
the pairs of chromatids (daughter chromosomes) go on microtubule track to the poles
telophase
spindle breaks down
chromosomes uncoil and are less condensed
nuclear envelopes and nucleoli reform,
how does cytokinesis happen in animals
what’s it called
contraction of cytoplasmic microfilaments, it separates the cytoplasms of 2 daughter cells
plasma membrane furrowing/ cleavage
how does cytokinesis happen in plants
vesicle fusion forming the cell plate (new cell wall)
what type of reproduction is mitosis, who uses it?
asexual reproduction
unicellular org. reproducing or multicell org. breaks off to from new individual
how could there be genetic variety in mitosis
mutations
because theyre clones
what are somatic cells
2n diploid (2 sets of chromosomes) not for reproduction
they hav homologous pairs of chromosomes with the corresponding gene (=size,shape, info)
each parent gives one homolog
what are gametes
sperm/egg
- haploid n (one set of chromo) for reproduction
- half of the parents chromo are randomly taken, every kid will be different)
what is it when 2 gametes (boy+girl) meat and fuse to form diploid zygote cell
fertilization
name the sexual life cyckes
haplontic life cycle
alternation of generations
diplontic life cycle
what is haplontic life cycle
a sexual life cycle
fungus/protist use it
zygote is only 2n stage
what is alteration of generations
sexual life cycle
plants and photosythetic protist
meiosis makes n spores
1/2 haploid 1/2 diploid
what is diplontic life cycle
sexual life cycle
animals use it
gametes are only n stage
how Many times does the meiosis do nuclear /? and y?
2 times
to make chromosomes haploid
prophase 1 (meiosis)
homologous chromosomes pair up
material is exchanged cy crossing over (recombination) between non sister chromatids of adjacent homologs
what follows telophase 1 in meiosis
interkinesis (its its interphase)
DNA can replicate now
how many cells are made from meiosis
4
what is nondisjunction
one homologous pair of chromosmes dont separate from each other and both go to same pole (mitosis 1)
OR sister chromatids dont separate (mitosis 2)
what are the effects when nondisjunction occurs
one gamete has and extra chromosome -> trisomy
one gamete is lacking a chromosome -> monosomy
if fertilized with normal gamete it crates aneuploidy
karyotype
the number, shapes, and sizes of the chromosomes in a cell
how to recognize individual chromosomes from each other
LENGTHS, POSISITON OF CENTROMERE BANDING PATTERNS
