Ch. 5 - Cell Division

Question 1

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)

Answer 1

_____
homologous chromosomes
23
92

Question 2

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 _____.

Answer 2

centrosomes
outside
pair
centrioles

Question 3

Prophase: nucleus disassembles: _____ disappear, chromatin condenses into _____, and nuclear envelope
breaks down. _____ is formed and microtubules (composed of tubulin) begin connecting to kinetochores.

Answer 3

_____
nucleoulus
chromosomes
mitotic spindle

Question 4

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.

Answer 4

count centromeres

karyotyping

Question 5

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.

Answer 5

disjunction

Question 6

Telophase: nuclear division, nuclear envelop develops, chromosomes => _____, nucleoli _____.

Answer 6

_____
chromatin
reappear

Question 7

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 _____.

Answer 7

actin
microfilaments

Golgi bodies
separate
cements adjacent cells together

Question 8

Cell cycle = _____ phases

Answer 8

M, G1, G2, S

Question 9

During G1, cell _____ in size, and the G1 checkpoint ensures everything is ready for _____

Answer 9

increases

DNA synthesis

Question 10

During S phase, second molecule of DNA replicated from _____, provides _____ – DNA synthesis

Answer 10

the first

sister chromatids

Question 11

During G2, _____ cell growth, preparation for of genetic material for _____

Answer 11

rapid

cellular division

Question 12

More time spent in _____ than mitosis (>90%). Growth occurs in all _____, not just G’s.

Answer 12

interphase

interphases

Question 13

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 _____

Answer 13

G1
G0
Mitosis Promoting Factor (MPF)
G1

Question 14

• Meiosis I: _____ pair at plate, migrate to opposite poles (no _____ of sister chromatids).

Answer 14

homologous chromosomes

separation

Question 15

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 _____

Answer 15

homologous chromosomes
tetrads

chiasmata

protein structure
tetrad w/ chiasmata
crossing over

Question 16

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)

Answer 16

leptotene
zygotene
pachytene
diplotene
diakinesis

Question 17

Metaphase I: homologous pairs are spread across metaphase plate. Microtubules attached to kinectochores of _____. Microtubules from other site attach to 2nd member of pair.

Answer 17

one member of each homologous pair

Question 18

Anaphase I: homologues within tetrads uncouple and pulled to opposite sides (_____)

Answer 18

disjunction

Question 19

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.

Answer 19

half number of chromosomes
reduction phase
interphase

Question 20

• Meiosis II: chromosomes spread across metaphase plate and sister chromatids separate and migrate to opposite poles. It is similar to _____ .

Answer 20

mitosis

Question 21

Prophase II: nuclear envelop disappears and spindle develops etc, no _____ and no _____.

Answer 21

chiasmata

crossing over

Question 22

Metaphase II: chromosomes align on plate like in mitosis but now with _____ (no extra copy).

Answer 22

half number of chromosomes

Question 23

Anaphase II: each chromosome is pulled into _____ and migrate to opposite poles of cell

Answer 23

2 separate chromatids

Question 24

Telophase II: nuclear envelope reappears and cytokinesis occurs => _____ (each chromosome = 1 chromatid).

Answer 24

4 haploid cells

Question 25

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.

Answer 25

sporangia
spores
gametophyte
sporophyte

Question 26

Alternation of generations: Alternation of _____ and _____ stages.

Answer 26

diploid

haploid

Question 27

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)

Answer 27

prophase I
independent assortment of homologues
random joining
genetic composition

Question 28

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.

Answer 28

exchange
cell death
cell divison

Question 29

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.

Answer 29

constant
volume
exceed the ability
regulator
multinucleated

Question 30

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.

Answer 30

restriction point

divide

Question 31

G2 Checkpoint: end of G2 phase, evaluates accuracy of _____ and signal whether to begin mitosis.

Answer 31

DNA replication

Question 32

M Checkpoint: during metaphase, ensures _____ are properly attached to all kinetochores. Prevents _____ if not.

Answer 32

microtubules

anaphase

Question 33

Cyclin-dependent kinases (Cdk’s): Cdk enzyme activates proteins that _____ by phosphorylation; Cdk’s are activated by protein _____.

Answer 33

regulate cell cycle

cyclin

Question 34

Growth Factor: plasma membrane has receptors for growth factors that _____ (such as damaged cell)

Answer 34

stimulate cell for divison

Question 35

Density-dependent inhibition: cells stop _____ when surrounding cells _____ reaches maximum.

Answer 35

dividing

density

Question 36

Anchorage dependence: most cells only divide when attached to an _____ such as _____ or side of culture dish.

Answer 36

external surface

neighboring cells

Question 37

Cancer cells defied all of the _____ above (such cells are called transformed cells).

Answer 37

5 conditions: cell checkpoints, Cdk’s, growth factors, density dependent inhibition, anchorage dependence

Question 38

Cancer drugs that inhibit mitosis do so by disrupting the ability of _____ to separate chromosomes during anaphase, stopping _____

Answer 38

microtubules

replication

Question 39

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

Answer 39

mitosis

doubled

Question 40

Joining of gametes is _____, but some sperm cells contain genetic material that gives them a _____ – so they aren’t all _____ competitive

Answer 40

random
competitive advantage
equally

Question 41

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?)

Answer 41

cytokinesis