chapter 7: cell cycle + cell division Flashcards
alternation of generations
most plants
meioisis->haploid spores->mitosis->gametophyte->mitosis->gametes->gametes fuse to create zygote->mitosis->diploid sporophyte
back to meiosis
haplontic organisms
zygote is the only diploid cell.
once formed, meiosis->haploid cells, usually spores
spores are germinated to form new haploid organism
diplontic organisms
gametes are the only haploid cells
mature organism is diploid
sexual reproduction
random selection of half of the diploid chromosome set to make a haploid gamete
then diffusion of haploid gametes from separate parents to form diploid cell
segregation
- part of cell division where replicated dna is distributed to the two new cells
- ori regions move to opposite ends of cell
- active process
cell division
- reproductive signal
- replication of dna
- segregation of dna
- cytokinesis
binary fission
cell division in prokaryotes
prokaryotic chromosome
ori: origin of replication site
ter: termination site of replication
mitosis, then cutokinesis
- cell division in eukaryotic cells
- requirements:
1. replication of dna
2. segregation of dna, then mitosis
3. cytokinesis
interphase
g1 (g0). s, g2 phases
prophase
- first stage of mitosis
- condensed chromosomes
- centrosome (determines spatial relationship of two new cells)
- spindle
kinetochores
- specialized proteins on the centromeres of sister chromatids that help with movement
- are involved withe condensed chromosomes during prophase
karyotype
number and size of condensed chromosomes
can identify organisms by it
prometaphase
nuclear envelop breaks down
metaphase
chromosomes line up at midline of cell, equatorial position
anaphase
chromatids separate and daughter chromosomes move away from each other toward poles
polar microtubules
- form framework of spindle
- from pole to pole, keepinf them apart
kinetechore microtubules
- become attached to sister chromatids from opposite sides of cell
- acts as molecular motor, pulling them away from each other toward poles
telophase
nuclear envelope forms around each new set of chromosomes
—>two new nuclei in cell
contractile ring
furrow of cytokinesis in animal cells, pinching the cell in two
cell plate
beginning of new cell wall during cytokinesis of plants
growth factors
signal to stimulate cell division/differentiation in eukaryotic cells
cyclin-dependent kinase
-enzyme that regulates cell cycle
growth factor->cyclin synthesis->cdk activation-> cell cycle events
functions of meiosis
- reduce chromosome number from diploid to haploid
- ensures haploid products have complete set of chromosomes
- genetic diversity
meiosis 1
- homologous chromosomes come together and line up
- homologous chromosome pairs separate, but the individual chromosomes (each consisting of 2 sister chromatids) remain intact
meoisis 2
separates sister chromatids
result: 4 genetically different cells
crossing over
- chiasma=points at which homologous chromosomes are attached
- genetic marerial is exchanged
- results in recombinant chromatids (genetic variation)
independent assortment
- different possibilities of lineup at metaphase 1
- total chance for which homologous pair goes to which daughter cell
nondisjunction
-meiotic error where homologous chromosome pair fails to separate in anaphase 1 or chromatids dont separate in anaphase 2
aneuploidy
when nondisjuntion causes trisomy (having extra chromosome) or monosomy (missinf chromosome)
polyploidy
- meiotic error when triploid, tetraploid, or higher order polyploid nuclei form
- can occur if there is an extra round of dna replication or no spindle formation
- occurs naturally in some animals, leads to speciation
translocation
- meiotic error when chromatids from homologous chromosomes pairs break and rejoin
- changes location of genes relative to other dna sequences
necrosis
- when cells are damaged by mechanical means or starved of nutrients
- cells swell and burst
apoptosis
- genetically programmed series of events that cause cell death, aka cell suicide
- cell detaches from neighbors, hydrolizes dna into small fragments, and breaks these fragments up
- reasons:
1. cell is no longer needed
2. the older the cell, the more prone it is to genetic damage that could lead to cancer
hypersensitive response
when plants use apoptosis to protect themselves from disease
caspases
enzymes that are important to apoptosis because they hydrolyze the target molecules
oncogene
- positive regulators of cell cycle in cancer cells
- stimulate cancer cells to divide more often
tumor suppressors
- negative regulators of cell cycle in normal cells, but are inactive in cancer cells
- tells cell cycle to not proceed
