Topic 4 (pre-exam)

Question 1

how often does the cell cycle occur, and how long does each stage last?

Answer 1

once approximately every 24 hours (circadian rhythms)

interphase - G1: 11 hours; S: 8 hours; G2: 4 hours
mitosis - 1 hour

Question 2

role of S phase and G2 phase in the cell cycle

Answer 2

prepare the cell for division (mitosis)

Question 3

what is the best way to distinguish living/nonliving matter?

Answer 3

cell division; continuity of life based on the reproduction of cells

Question 4

cell division in unicellular organisms

Answer 4

cell division is reproduction; division of one cell replicates the entire organism

Question 5

purpose of cell division in multicellular organisms

Answer 5

needed for:

• development of a fertilized cell
• growth
• repair (i.e. tissue renewal)

Question 6

what is the result of mitotic vs meiotic cell division?

Answer 6

mitotic: daughter cells with identical genetic info (DNA) and 2 sets of chromosomes
meiotic: nonidentical daughter cells (gametes aka sperm and egg cells) with only 1 set of chromosomes

Question 7

genome

Answer 7

all of the DNA in a cell (including in mitochondria and/or chloroplasts)

*can consist of a single DNA molecule (prokaryotes) or a number of DNA molecules eukaryotes)

Question 8

function and significance of chromosomes

Answer 8

DNA is condensed and packaged into chromosomes (with proteins) during prophase

*every eukaryotic species has a characteristic number of chromosomes in each cell nucleus

Question 9

somatic cells vs gametes

Answer 9

somatic cells: non-reproductive; 2 sets of chromosomes

gametes: reproductive; half the chromosomes

Question 10

chromatin

Answer 10

complex of DNA and protein that condenses into chromosomes during cell division; makes up eukaryotic chromosomes

Question 11

what occurs in preparation for cell divison?

Answer 11

DNA is replicated and chromosomes condense

Question 12

sister chromatids

Answer 12

the 2 identical copies of a chromosome after it’s been duplicated that separate during cell division

Question 13

centromere

Answer 13

the narrow waist of a duplicated chromosome, tightly attaches sister chromatids

Question 14

two phases of eukaryotic cell division

Answer 14

mitosis - division of nucleus

cytokinesis - division of cytoplasm

Question 15

historical breakthrough in observing the cell cycle

Answer 15

Walter Flemming developed dyes to observe chromosomes and see their change in form, called the “father of cytogenics”

*various staining techniques today to observe chromosomes

Question 16

two parts of the cell cycle and their functions:

Answer 16

Mitotic (M) phase - mitosis and cytokinesis

Interphase - cell growth and copying of chromosomes in preparation for cell division

Question 17

phases of mitosis

Answer 17

prophase, prometaphase, metaphase, anaphase, telophase

• cytokinesis underway by late telophase
• process is still a continuum!!

Question 18

prophase

Answer 18

assembly of mitotic spindle

• DNA condenses into chromosomes
• nuclear envelope disappears
• centrosome (outside of nuclear envelope) replicates in 2; migrates to opposite ends of cell
• spindle microtubules are assembled and begin to grow out of centrosomes
• asters extends from each centrosome

Question 19

centrosomes

Answer 19

• both create and control microtubules

- discovered by Walther Flemming; only in animal cells (unknown where plant microtubules come from)

Question 20

mitotic spindle

Answer 20

made of up centrosomes, spindle microtubules, and asters

Question 21

asters

Answer 21

radial array of short microtubules extending from each centrosome

Question 22

types of microtubules

Answer 22

spindle microtubules

• kinetochore: attach to kinetochore of chromosomes during prometaphase to pull chromosomes apart during anaphase
• nonkinetochore: overlap and push against eachother during telophase to elongate cell

other microtubules
- asters: short microtubules that anchor spindle posts to cell membrane

Question 23

prometaphase

Answer 23

spindle microtubules attach to kinetochores of chromosomes and begin to move them

Question 24

kinetochores

Answer 24

complex of proteins associated with the centromere of chromosomes where spindle fibers attach

Question 25

metaphase

Answer 25

chromosomes lined up at metaphase plate (cell equator) midway between spindle's 2 poles

Question 26

anaphase

Answer 26

sister chromatids separate and move along kinetochore microtubules towards opposite ends of cell - microtubules shorten by depolymerizing at kinetochore ends

Question 27

telophase

Answer 27

nonkinetochore microtubules from opposite poles overlap and push against each other, elongating cell - genetically identical daughter nuclei form at opposite ends of cell

Question 28

how did scientists learn how kinetochores depolymerize?

Answer 28

- scientists used a pig kidney cell in early anaphase - spindle microtubules dyed and part was lasered to remove fluorescence - they monitored change in length on either side of the mark as the chromosomes moved towards the poles - microtubules on kinetochore side shortened, so depolymerization happens at kinetochore end

Question 29

cytokinesis (plants vs animals)

Answer 29

- in animal cells: cleavage furrow forms | - in plant cells: more rigid, so a cell plate forms to divide them

Question 30

binary fission

Answer 30

- method of prokaryote reproduction | - chromosome replicates and 2 daughter chromosomes actively more apart

Question 31

evolution of mitosis

Answer 31

- mitosis evolved form binary fission because prokaryotes existed before eukaryotes - some protists exhibit "in-between" types of cell division

Question 32

what is the molecular control system?

Answer 32

chemical signals in the cytoplasm cause the frequency of cell division to vary with cell type

Question 33

evidence for regulation of cell division coming from the cytoplasm

Answer 33

- mammalian cells at different phases of the cell cycle were fused to form a single cell with 2 nuclei - when cells in S and G1 fused, nucleus of G1 cell immediately entered S phase and DNA synthesized - when cells in M and G1 fused, nucleus of G1 cell began mitosis (spindle formed and chromatin condensed) even though chromosomes had not been duplicated

Question 34

cell cycle control system

Answer 34

directs the sequential events in the cell cycle (like a clock) - both internal and external controls - specific checkpoints control where cell cycle stops until go-ahead signal received

Question 35

important checkpoints in cell cycle control system

Answer 35

most important: G1 checkpoint - cells that get go-ahead will complete other phases and divide; cells that don't get go-ahead signal will exit the cycle and switch into a non-dividing state called G0 phase G2 checkpoint - gives ok for cell division; right before M phase

Question 36

G0 phase

Answer 36

non-dividing state if no go-ahead signal is received at the G1 checkpoint

Question 37

regulatory proteins involved in cell cycle control

Answer 37

cyclins and cyclin-dependent kinases (Cdks) | - actively fluctuate levels during the cell cycle

Question 38

role of MPF

Answer 38

MPF (maturation-promoting-factor) is a cyclin-Cdk complex that gives the cell the go-ahead past the G2 checkpoint, stimulating the mitotic (M) phase - once mitosis completed, cyclins degrade from MPF

Question 39

equation for determining concentrations

Answer 39

C1V1 = C2V2

Question 40

examples of internal cell signaling

Answer 40

when kinetochores not attached to the spindle, a signal is sent to delay anaphase

Question 41

examples of external cell signaling relating to mitosis

Answer 41

growth factors - proteins from some cells stimulate other cells to divide - platelet-derived growth factor (PDGF) - stimulates division of human fibroblast cells density-dependent inhibition - crowded cells stop dividing

Question 42

anchorage dependence

Answer 42

cells must be attached to a substratum in order to divide (most animal cells) *cancer cells often don't have this

Question 43

characteristics of cancer cells

Answer 43

- no density-dependent inhibition nor anchorage dependence - don't respond to cell cycle control mechanisms - may not need growth factors to divide (make their own growth factor, convey growth signal without factor, or have abnormal control system)

Question 44

transformation

Answer 44

process by which normal cells transformed to cancerous cells

Question 45

what do cancer cells do? why are they dangerous?

Answer 45

form tumors - masses of abnormal cells within otherwise normal tissue ***can invade healthy tissue (disrupting functions of organs) and take resources away from the cell