Studied by 19 peopleWhat are the two general steps in cell division?
karyokinesis (nuclear division)
cytokinesis
How many copies of each chromosome are there in diploid cells?
2
(Note: pairs of homologous chromosomes)
How many total chromosomes do humans possess in somatic cells?
46
(Note: 23 homologous pairs)
How many homologous pairs do humans possess?
23
How many chromatids do humans possess?
92
(Note: total chromosomes x 2)
What cell division do all body cells, or somatic cells undergo?
mitosis
Which structures play a large part in cell division by orienting genetic material?
microtubule organizing centers (MTOCs)
Each MTOC contains a pair of ____________.
centrioles
What are the characteristic steps of mitosis?
prophase
metaphase
anaphase
telophase
cytokinesis (mnemonic: P-MAT-C)
During prophase, what occurs in the nucleus?
disassembles
During prophase, what occurs in the nucleolus?
disappears
During prophase, what occurs in the chromatin?
condenses into chromosomes
During prophase, what occurs in the nuclear envelope?
breaks down
What organizing apparatus forms during prophase?
mitotic spindle
During prophase, microtubules begin connecting to which structures?
kinetochores
During metaphase, where do chromosomes line up?
equator
During metaphase, where are centrosomes located?
opposite poles
In which step of mitosis is karyotyping performed?
metaphase
Sister chromatids separate during which step of mitosis?
anaphase
(Note: VERY IMPORTANT - chromosome number doubles during anaphase)
During anaphase, what happens to microtubules?
shorten
Sister chromatids
chromosomes
(Note: new chromosomes are technically halves of the chromosomes found in metaphase)
After anaphase, What is the total chromosome number in the somatic cell?
92
What is the process called when microtubules pull the chromosomes to opposite poles of the cell during anaphase?
disjunction
In which step of mitosis does nuclear division occur?
telophase
During telophase, what structure forms around the groups of separated chromosomes?
nuclear envelope
During telophase, what occurs in the chromosomes?
they unravel
Which stage in mitosis involves the division of cytoplasm to form two cells?
cytokinesis
During the cytokinesis step in animal cells, what is the name for the invagination that forms?
cleavage furrow
How is the cleavage furrow formed?
shortening of actin and myosin microfilaments
During the cytokinesis step in plant cells, what divider forms?
cell plate
what structures migrate and fuse to form the cell plate in plant cell mitosis?
vesicles from Golgi bodies
As the cell plate grows, what structure does it merge with?
plasma membrane
What are the phases of the cell cycle?
G1 (growth)
S (DNA synthesis)
G2 (growth)
M (mitosis)
During G1, how does the size of the cell change?
it increases
What structures are synthesized in large quantities during G1?
proteins and ribosomes
What step ensures that everything is ready for DNA synthesis during the cell cycle?
G1 checkpoint
Which phase of the cell cycle is the most variable in length of all the phases depending on the cell type?
G1
In which phase of the cell cycle is DNA replicated?
S
(Note: provides sister chromatids)
In which phase of the cell cycle does rapid cell growth occur, organelles are replicated, and genetic material prepares for cell growth?
G2
Which phases of the cell cycle constitute interphase?
G1, S, and G2
What percentage of the cell cycle is interphase?
90%
Growth occurs during which cell cycle phases?
all interphase phases
(Note: not just G phases)
What steps occur to ensure that every cell cycle phase is occurring smoothly and as planned?
checkpoints
What is the first and most important checkpoint in the cell cycle?
G1 checkpoint
If the G1 checkpoint fails, the cell enters what state?
G0
What type of state is G0?
non-dividing
Which cells can be induced out of G0?
liver
kidney
Which cells permanently reside in G0 if they enter the phase?
nerve and muscle cells
Which checkpoint of the cell cycle ensures there is sufficient mitosis promoting factor (MPF) levels to proceed to mitosis ?
G2
The accuracy of which process is checked at the G2 checkpoint?
DNA replication
Which checkpoint of the cell cycle determines if all chromosomes are attached to kinetochores?
M
(Note: before G1 during mitosis)
What enzymes activate proteins that regulate the cell cycle via phosphorylation?
cyclin-dependent kinases (CDKs)
CDKs are activated by what molecules?
protein cyclins
(Note: vary in type and concentration throughout each phase of the cell cycle)
The plasma membrane contains receptors for which regulator that stimulates cell division?
growth factor
What process stops cells from dividing when the surrounding cell density reaches a maximum?
density-dependent inhibition
What is the phenomenon that most cells only divide when they are attached to an external surface?
anchorage dependence
Which cells defy CDKs, growth factors, density-dependent inhibition, and anchorage dependence?
cancer cells
What are the steps of meiosis?
meiosis I and meiosis II
(Note: each have similar steps to mitosis)
How many chromosomes/chromatids are present after interphase before meiosis I begins?
46 chromosomes 92 chromatids
Which step in meiosis I involves nuclear material breaking down, chromatin condensing, and the mitotic spindle development?
prophase I
What action do the microtubules perform in prophase I?
attach to kinetochores
What is the process that involves homologous chromosomes pairing up, forming a tetrad (two bivalents)?
synapsis
What is a tetrad?
group of 4 chromatids
What process allows genetic recombination to occur in prophase I?
crossing over
What is the region where crossing over of non-sister chromatids occurs?
chiasmata
What is the protein structure that temporarily forms between homologous chromosomes during prophase I?
synaptonemal complex
(Note: gives rise to tetrad with chiasmata and crossing over)
What are the 5 stages of prophase I?
leptotene
zygotene
pachytene
diplotene
diakinesis
Which stage of prophase I involves chromosomes condensing?
leptotene
Which stage of prophase I involves synapsis beginning and the synaptonemal complex forming?
zygotene
Which stage of prophase I involves completed synapsis and crossing over?
pachytene
Which stage of prophase I involves the synaptonemal complex disappearing, but chiasma is still present?
diplotene
Which stage of prophase I involves nuclear envelope fragmenting and completed chromosome condensing?
diakinesis
Which step of meiosis I includes microtubules attaching to kinetochores of each homologous pair?
prophase
Which step of meiosis I includes homologous pairs pulling to opposite sides (disjunction)?
anaphase I
Which step of meiosis I has nuclear membrane develops and each pole forms a new nucleus with half the number of chromosomes?
telophase I
how many chromosomes/chromatids are present after meiosis I?
23 chromosomes 46 chromatids
(Note: 2 cells with these numbers)
What step of meiosis II has the nuclear envelope disappear and the spindle develop?
prophase II
What is the major difference between prophase II and prophase I
no crossing over in prophase II
Which step of meiosis II has the chromosomes lining up across the equator of each cell?
metaphase II
Which step of meiosis II has each chromosome pulled into 2 separate chromatids and migrate to opposite poles of the cell?
anaphase II
(Note: still same number of chromosomes in each cell, just half the chromatids)
Which step of meiosis II has the nuclear envelope reappearing and cytokinesis occurring?
telophase II
how many chromosomes/chromatids are present after meiosis II?
23 chromosomes 23 chromatids
(Note: 4 haploid cells with these numbers)
In plants, meiosis in sporangia produces what reproductive unit?
spores
(Note: haploid)
What process do haploid spores undergo to become multicellular haploid gametophytes?
mitosis
A plant's multicellular haploid gametophytes fuse together to form what reproductive unit?
diploid zygote
How does a plant's diploid zygote transition to a sporophyte?
mitosis
Cells in plants' sporophyte (sporangia) undergo what process to produce haploid spores that germinate and repeat the life cycle?
meiosis
(Note: known as alteration of generations)
What are the 2 main ratios that dictate if a cell will divide
surface to volume ratio
genome to volume ratio
What surface to volume ratio is favorable for cell division?
small SA:V
Why would a cell not want to divide if SA:V is high?
exchange across cell is easy
(Note: no need to divide)
What genome to volume ratio is favorable for cell division?
small G:V
Why would a cell need to divide if G:V is small?
the genome cannot regulate cell activities
(Note: some cells are multinucleate to deal with this)
Which version of cell division results in genetic variety?
only meiosis
homologous chromosomes
centromere
kinetochore
synaptonemal complex
Note
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