Ch. 5 - Cell Division Flashcards
In diploid cells, there are two copies of every chromosome, forming a pair (_____). Human have 46 chromosomes, _____ homologous pair, a total of _____ chromatids (depending on stage of division1)
_____
homologous chromosomes
23
92
MTOCs: Microtubule organizing centers aka _____. Pair of these lay _____ nucleus. In animal cells, each MTOC contains a _____ of centrioles. Recall that plants do have MTOC’s called centrosomes, but they aren’t composed of _____.
centrosomes
outside
pair
centrioles
Prophase: nucleus disassembles: _____ disappear, chromatin condenses into _____, and nuclear envelope
breaks down. _____ is formed and microtubules (composed of tubulin) begin connecting to kinetochores.
_____
nucleoulus
chromosomes
mitotic spindle
Metaphase: chromosomes line up single file at center, each chromatid is complete with a centromere and a kinetochore, once separated, it is a chromosome (to keep track of total: _____). Centrosomes at opposite ends of cell. (note: once separated that’s the end of metaphase, so to be precise the chromosome # doubles at anaphase). _____ performed here.
count centromeres
karyotyping
Anaphase: microtubules shorten, each chromosome is pulled apart into two chromatids (once separated it is a chromosome; chromosome # doubles), pulls the chromosomes to opposite poles (_____); at the end of this phase, each pole has a complete set of chromosome, same as original cell before replication.
disjunction
Telophase: nuclear division, nuclear envelop develops, chromosomes => _____, nucleoli _____.
_____
chromatin
reappear
Cytokinesis: Actually begins during the later stages of mitosis (most sources indicate it begins towards the end of
anaphase). Division of cytoplasm to form 2 cells.
- Cleavage furrow: _____ and myosin _____ shorten, pull plasma membrane into center (animal)
Note: begins formation during anaphase? - Cell plate: vesicles from _____ migrate and fuse to form cell plate, out growth and merge with plasma membrane separating the two new cells (plants). Cells don’t actually _____ from each other, middle lamella _____.
actin
microfilaments
Golgi bodies
separate
cements adjacent cells together
Cell cycle = _____ phases
M, G1, G2, S
During G1, cell _____ in size, and the G1 checkpoint ensures everything is ready for _____
increases
DNA synthesis
During S phase, second molecule of DNA replicated from _____, provides _____ – DNA synthesis
the first
sister chromatids
During G2, _____ cell growth, preparation for of genetic material for _____
rapid
cellular division
More time spent in _____ than mitosis (>90%). Growth occurs in all _____, not just G’s.
interphase
interphases
There are checkpoints in these cycles to make sure things are going as planned
o Near the end of _____ – cell growth assessed and favorable conditions checked. If fails, cell enters _____
o End of G2 – checks for sufficient _____ levels to proceed
o M checkpoint (metaphase checkpoint) during mitosis that triggers start of _____
G1
G0
Mitosis Promoting Factor (MPF)
G1
- Meiosis I: _____ pair at plate, migrate to opposite poles (no _____ of sister chromatids).
homologous chromosomes
separation
Prophase I: nucleus disassembles: nucleolus disappears and nuclear envelop breaks down, chromatin condenses, spindle develops. MT’s begin attaching to kinetochores. Crossing over means genetic recomb, NT seq. might change!
- Synapsis: _____ pair up. These pairs are referred to as _____ (group of 4 chromatids) or bivalents.
- _____: region where crossing over occur of non-sister chromatids.
- Synaptonemal complex: _____ that temporarily forms between homologous chromosomes: gives rise to the _____ and _____
homologous chromosomes
tetrads
chiasmata
protein structure
tetrad w/ chiasmata
crossing over
Prophase I has 5 steps:
_____ (chromosomes start condensing)
_____ (synapsis begins; synaptonemal complex forming)
_____ (synapsis complete, crossing over)
_____ (synatopnemal complex disappears, chiasma still present)
_____ (nuclear envelope fragments, chomosomes complete condensing, tetrads ready for metaphase)
leptotene zygotene pachytene diplotene diakinesis
Metaphase I: homologous pairs are spread across metaphase plate. Microtubules attached to kinectochores of _____. Microtubules from other site attach to 2nd member of pair.
one member of each homologous pair
Anaphase I: homologues within tetrads uncouple and pulled to opposite sides (_____)
disjunction
Telophase I: nuclear membrane develops. Each pole forms a new nucleus that has _____ (from homologous pair to each chromosome = 2 sister chromatids). Chromosomes _____ to haploid.
- _____ may occur in between here, depending on the species.
half number of chromosomes
reduction phase
interphase
- Meiosis II: chromosomes spread across metaphase plate and sister chromatids separate and migrate to opposite poles. It is similar to _____ .
mitosis
Prophase II: nuclear envelop disappears and spindle develops etc, no _____ and no _____.
chiasmata
crossing over
Metaphase II: chromosomes align on plate like in mitosis but now with _____ (no extra copy).
half number of chromosomes
Anaphase II: each chromosome is pulled into _____ and migrate to opposite poles of cell
2 separate chromatids
Telophase II: nuclear envelope reappears and cytokinesis occurs => _____ (each chromosome = 1 chromatid).
4 haploid cells
In plants, meiosis in _____ produces _____ (haploid); spores undergoes mitosis to become multicellular (_____) which are haploid (n) since spores are already haploid. The gametes fuse and produce a diploid cell (zygote 2n) that grows by mitosis to become _____. Cells in sporophyte (_____) undergoes meiosis to produce haploid spores which germinate and repeat life cycle.
sporangia
spores
gametophyte
sporophyte
Alternation of generations: Alternation of _____ and _____ stages.
diploid
haploid
Genetic Variation: Genetic recombination during meiosis and sexual reproduction originates from three events:
Crossing over during _____
_____ during metaphase I (which chromosome goes into which cell)
_____ of gametes aka germ cells (which sperm fertilizes which egg – _____ of gamete affects this)
prophase I
independent assortment of homologues
random joining
genetic composition
REGULATION OF CELL CYCLE functional limitations
Surface-to-volume ratio (S/V): volume gets much larger when cells grow ( (4/3)𝜋𝑟^3) vs. SA (4 𝜋𝑟^2). When S/V is large, _____ becomes much easier. When S/V is small, exchange is hard, leads to _____ or _____ to increase SA.
exchange
cell death
cell divison
REGULATION OF CELL CYCLE functional limitations
Genome-to-volume ratio (G/V): genome size remains _____ throughout life; as cell grows, only _____ increases. G/V will be small and thus _____ of its genome to produce sufficient amounts of _____ of activities. Some large cells (paramecium, human skeletal muscle) are _____ to deal with this.
constant volume exceed the ability regulator multinucleated
1. G1 Checkpoint: aka \_\_\_\_\_, the most important one. At the end of G1 phase, if cell is not ready to \_\_\_\_\_ it may arrest here (G0 phase – nerve and muscle cells remain here, rarely divide after maturing) and never proceed or wait until it is ready.
restriction point
divide
G2 Checkpoint: end of G2 phase, evaluates accuracy of _____ and signal whether to begin mitosis.
DNA replication
M Checkpoint: during metaphase, ensures _____ are properly attached to all kinetochores. Prevents _____ if not.
microtubules
anaphase
Cyclin-dependent kinases (Cdk’s): Cdk enzyme activates proteins that _____ by phosphorylation; Cdk’s are activated by protein _____.
regulate cell cycle
cyclin
Growth Factor: plasma membrane has receptors for growth factors that _____ (such as damaged cell)
stimulate cell for divison
Density-dependent inhibition: cells stop _____ when surrounding cells _____ reaches maximum.
dividing
density
Anchorage dependence: most cells only divide when attached to an _____ such as _____ or side of culture dish.
external surface
neighboring cells
Cancer cells defied all of the _____ above (such cells are called transformed cells).
5 conditions: cell checkpoints, Cdk’s, growth factors, density dependent inhibition, anchorage dependence
Cancer drugs that inhibit mitosis do so by disrupting the ability of _____ to separate chromosomes during anaphase, stopping _____
microtubules
replication
Keep in mind that if you are seeing chromosomes, that means the chromatin has condensed already so you’re looking at _____ occurring – so if asked the number of chromatids, assume they’ve already been _____ in this situation
mitosis
doubled
Joining of gametes is _____, but some sperm cells contain genetic material that gives them a _____ – so they aren’t all _____ competitive
random
competitive advantage
equally
Chad’s says that during meiosis, _____ varies among species – can occur at end of Telophase I, end of meiosis, etc. (seems to occur during both in humans?)
cytokinesis
