Cell Division

_____ is nuclear division (karyokinesis) followed by cytokinesis

cell division

_____ is the nuclear division of cell division

karyokinesis

_____ is the division of the cytoplasm that happens at the end of cell division

cytokinesis

in _____ cells, there are 2 copies of every chromosome, forming a pair called _____ chromosomes

diploid; homologous

humans have _____ chromosomes, _____ homologous pairs, and a total of 92 chromatids (depending on the stage of division)

46, 23

humans have 46 chromosomes, 23 homologous pairs, and a total of _____ chromatids (depending on the stage of division)

92

a _____ is 1 of 2 identical parts of a duplicated chromosome

chromatid

microtubule organizing centers (MTOCs) are called _____ in animal cells

centrosomes

(MTOCs are just called MTOCs in plants/fungi)

MTOCs are found outside the _____ during interphase

nucleus

centrosomes (animal cell MTOCs) contain a pair of _____

centrioles

usually there is _____ MTOC per cell; however, cells replicate their MTOCs during _____

1; S phase

there are _____ MTOCs before cell division (after the S phase of interphase)

2

plants/fungi have MTOCs, but they are NOT _____

centrosomes

(plants/fungi just have "MTOCs")

_____ occurs in somatic cells and _____ occurs in gametes (egg, sperm, pollen)

mitosis; meiosis

mitosis occurs in _____ cells and meiosis occurs in _____ (egg, sperm, pollen)

somatic; gametes

what is fertilization?

the fusion of 2 haploid gamete nuclei to make 1 diploid zygote

_____ is the phase of cell division in which chromatin condenses into chromosomes

prophase

_____ is the phase of cell division, in which the nuclear envelope breaks down

prophase

_____ is the phase of cell division in which the mitotic spindle forms

prometaphase

microtubules begin connecting to kinetochores during _____ of cell division

prometaphase

_____ is the phase of cell division in which chromosomes line up in a single file in the center

metaphase

_____ is the phase of cell division in which each chromatid is complete with a centromere and attached kinetochore

metaphase

_____ is the phase of cell division in which replicated centrosomes are at opposite ends of the cell

metaphase

_____ is the phase of cell division in which karyotyping is performed

metaphase

_____ is a visual depiction of one's chromosomes by homologous pairs, and it is usually performed during metaphase

karyotyping

_____ is the phase of cell division in which kinetochore microtubules shorten

anaphase

_____ is the phase of cell division in which polar microtubules lengthen

anaphase

_____ is the phase of cell division in which each chromosome is pulled apart

anaphase

once separated at anaphase, each _____ is considered a _____

chromatid; chromosome

_____ is the phase of cell division in which chromosomes are pulled to opposite poles (disjunction)

anaphase

at the end of _____, each pole has a complete set of chromosomes

anaphase

what is the shortest step of cell division?

anaphase

_____ is the phase of cell division when karyokinesis occurs

telophase

(karyokinesis = nuclear division - notice the formation of 2 nuclei)

_____ is the phase of cell division in which the nuclear envelopes re-develop

telophase

_____ is the phase of cell division in which chromosomes de-condense back into chromatin

telophase

_____ is the phase of cell division in which nucleoli reappear

telophase

the presence of chromosomes means _____ is occurring

mitosis/meiosis

(cell division)

in metaphase, a chromosome consists of 2 closely attached _____

sister chromatids

the end of _____ is denoted by the presence of centrosomes at opposite ends of the cell

metaphase

to keep track of the total number of chromosomes during cell division, count the number of _____

centromeres

in _____, the chromosome number doubles

anaphase

at the end of _____, each pole has a complete set of chromosomes, same as the original cell before replication

anaphase

at the end of anaphase, there would be a total of _____ chromosomes (separated chromatids) if a cell has 46 chromosomes at the beginning

92

genetic variation occurs in _____, but not in mitosis

meiosis

unlike meiosis, NO _____ occurs in mitosis

genetic variation

during cytokinesis, animal cells separate via creation of the _____

cleavage furrow

during _____ in animals, actin and myosin microfilaments shorten and the plasma membrane is pulled into the center, creating a _____

cytokinesis; contractile ring/cleavage furrow

plant cells undergo cytokinesis via formation of a _____

cell plate

as plant cells undergo cytokinesis, vesicles from _____ migrate and fuse to form a cell plate

golgi bodies

during plant cell division, the cells don't actually separate from each other because the _____ cements adjacent cells together

middle lamella

_____ begins after mitosis and cytokinesis complete

interphase

only the somatic cells that divide by _____ undergo interphase

mitotic

gametes do undergo _____ after they are made

interphase

what are the phases of interphase?

G1 (possibly G0), S, and G2 phase

what are the 3 *main* phases of the cell cycle?

mitosis, cytokinesis, interphase

90% of the cell cycle is spent in _____

interphase

the phase of interphase in which a checkpoint ensures everything is ready for DNA synthesis

G1

in what phase of the cell cycle will DNA synthesis occur?

the S phase of interphase

a second molecule of DNA is replicated from the first to provide sister chromatids in the _____ of interphase

S phase

the phase of interphase in which rapid cell growth occurs

G2

the cell prepares its genetic material for cellular division during the _____ of interphase

G2 phase

cells replicate their organelles during the _____ phase

gap 2 (G2)

when surface/volume ratio is _____, cellular exchange becomes easier

large

when surface/volume ratio is _____, cellular exchange is hard, and leads to cell death or cell division to increase surface area

small

what happens as the genome/volume ratio decreases (volume gets bigger)?

the cell exceeds the ability of its genome to produce sufficient amounts of regulation for cellular activities

some large cells (paramecium, human skeletal muscle) are _____ to deal with problems associated with ever decreasing genome/volume ratios

multinucleated

what is the most important checkpoint of the cell cycle?

the G1 checkpoint

_____ is assessed and _____ conditions are checked during the G1 checkpoint

cell growth; favorable

what happens if the G1 checkpoint fails?

the cell enters G0

; ; if checkpoint fails, ; some cells (liver, kidney) can be induced out of G0, some stay permanently (nerve and muscle cells); cells can either never proceed or wait until the cell is ready

G₁

at the end of _____, the cell evaluates the accuracy of DNA replication and signals whether to begin mitosis; the cell checks for sufficient mitosis promoting factor (MPF) levels to proceed.

G₂

at the end of G₂, the cell evaluates the accuracy of DNA replication and signals whether to begin mitosis; the cell checks for sufficient _____ levels to proceed.

mitosis promoting factor (MPF)

_____ checkpoint occurs during metaphase; division stops if the chromosomes are not attached to spindle fibers; if all are attached, cell is allowed to proceed with anaphase.

M

_____ are enzymes that activate proteins, which regulate the cell cycle by phosphorylation.

cyclin-dependent kinases (cdk)

_____ is a protein that activates cyclin-dependent kinases

cyclin

the plasma membrane has receptors for _____ that stimulate cells for division (such as damaged cell).

growth factors

cells stop dividing when surrounding cell density reaches a maximum - this is called _____.

density-dependent inhibition

most cells only divide when attached to an external surface, such as neighboring cells or a side of culture dish - this is called _____.

anchorage dependence

cancer cells defy the five cell-specific regulations in place. Such cells are called _____ cells.

transformed

cancer drugs that inhibit mitosis do so by disrupting the ability of _____ to separate chromosomes during anaphase, thus stopping replication.

microtubules

cancerous cells are a manifestation of defective cell _____.

differentiation

in meiosis, crossing-over occurs during _____

prophase I

during meiosis, _____ is when the homologous chromosomes pair up. These pairs are referred to as tetrads (groups of 4 chromosomes) or bivalents.

synapsis

during meiosis, synapsis is when the homologous chromosomes pair up. These pairs are referred to as _____ (groups of 4 chromosomes) or _____.

tetrads, bivalents

during meiosis, the _____ is the region where crossing over occurs of non-sister chromatids.

chiasmata

in meiosis, the _____ is a protein structure that temporarily forms between homologous chromosomes. This gives rise to the tetrad with chiasmata and crossing over

synaptonemal complex

in meiosis, disjunction of homologues occurs during _____

anaphase I

the phase of meiosis in which each pole forms a new nucleus that now has half the number of chromosomes - chromosome reduction phase to haploid

telophase I

phase of meiosis in which nuclear envelope disappears, spindle develops, etc.

• no chiasmata

• no crossing over

prophase II

phase of meiosis in which chromosomes align on middle plate like in mitosis, but there are now half the number of chromosomes

metaphase II

phase of meiosis in which sister chromatids separate

anaphase II

phase of meiosis in which nuclear envelope develops and cytokinesis occurs to produce 4 haploid cells

telophase II

Dyads

Replicated chromosomes containing two sister chromatids that look like an "x"

Centromeres

Regions of DNA that connect sister chromatids in a dyad

Kinetochores

Proteins on the sides of centromeres that help microtubules pull sister chromatids apart during cell division

Humans are _____ because they contain two sets of chromosomes

diploid (46 chromosomes, 23 pairs)

Gametes are _____ cells

haploid (only contain one chromosome set (23 chromosomes))

Gametocyte

Eukaryotic germ cells that can either divide to form more gametocytes or produce gametes

Kinetochore microtubules

Extend from centrosomes and attach to kinetochores on chromosomes

Astral microtubules

Extend from centrosomes to the cell membrane to orient the spindle apparatus