AP Biology

Chapter 12:The Cell Cycle

Checkpoints(Is all going according to plan?)

.

MPF activity

G1 G2S MS MG2G1

M

Cyclin

Time

Fluctuation of MPF activity and cyclin concentrationduring the cell cycle

Rel

ativ

e co

nce

ntr

atio

n

.

Degradedcyclin

G2

checkpoint

S

M

G 2G 1

Cdk

Cyclin isdegraded

MPFCyclin

Cdk

Molecular mechanisms that help regulate the cell cycle

accum

ulatio

nC

yclin

.

Chromosomemovement

Microtubule Motorprotein

Chromosome

Kinetochore

Tubulinsubunits

.Cells anchor to dish surface anddivide (anchorage dependence).

When cells have formed a completesingle layer, they stop dividing(density-dependent inhibition).

If some cells are scraped away, theremaining cells divide to fill the gap andthen stop (density-dependent inhibition).

25 µmNormal mammalian cells

.

Cancer cells do not exhibitanchorage dependenceor density-dependent inhibition.

Cancer cells25 µm

Malignant cancer cells from the breast(See the ABNORMAL “crab” shape of the cells.)

Mutations and Cancer

Activeformof p53

DNADNA damagein genome

UVlight

Protein kinasesMUTATION

Defective ormissingtranscriptionfactor, such as p53, cannotactivatetranscription

Protein kinases(phosphorylationcascade)

Cell cycle-inhibitingpathway

Cell cycle-stimulatingpathway

Protein thatstimulatesthe cell cycle

NUCLEUS

DNA

Gene expression

Transcriptionfactor (activator)

Receptor

G protein

Growthfactor

MUTATIONHyperactiveRas protein(product ofoncogene)issues signalson its own

Protein thatinhibitsthe cell cycle

• Question: Lectins are naturally occurring plant proteins that help promote increased mitosis within plant root tips. These proteins influence the normal production of MPF within the root cells and thereby speed up the cell cycle. In no more than three sentences, state ONE similarity and TWO differences between Lectin influenced cells and cancer cells. (5 Points)

•

• Scoring Rubric: 1pt. Discussion of one similiarity• Possible discussion points: Increased cell cycle rate.• Cyclin production rate is altered.• 1pt. Discussion of difference number 1• 1pt. Discussion of difference number 2• Possible discussion points: Cancer does not respond to checkpoints.• Cancer does not have density dependent.• Cancer does not have anchorage dependence.• Cancer not normal function for cells. • Cancer affects normal cyclin production.• Cancer being caused by carcinogens, etc.• 1pt. Correct use of scientific terms.• 1pt. Answer has no more than three sentences. (Following Directions.)• • This question addresses Essential Knowledge: 2.D.3