Chapter 10 Part 3: Cancer, Molecular Regulation and Cell Cycle Dysregulation

Intracellular molecules

regulate the cell cycle: + or -

Cyclin

protein involved in moving to next step of process

Positive Regulators do what (EXAM)

Promote the movement to next step of the cell cycle

cyclins and cyclin-dependent kinases (Cdks)

Positive Regulators process (EXAM)

Cyclin levels rise → cyclin binds Cdk → active cyclin cdk complex → phosphorylates target proteins → cell cycle progression

Positive regulators: What happens after the cyclin level rises

Cyclin binds Cdk

Positive regulators: What happens after the cyclin binds cdk complex

Phosphorylates target proteins

Positive regulators: What happens after the phosphorylates target proteins

cell cycle progression

Cyclin concentrations _______, CDK levels are relativly ___

Rises, Stbale

EXAM Q: Positive regulators help move a cell to the next step of the cell cycle. Which sequence correctly describes the cyclin-Cdk pathway?

Cyclin levels rise → cyclin binds Cdk → the active cyclin-Cdk complex phosphorylates target proteins → cell-cycle progression.

Negative Regulatory molecules do what (EXAM)

Stops advancement of the cell cycle

• Rb, p53, and p21 halt the cycle when DNA damage or errors are detected.

Best understood Negative regulatory molecules

Retinoblastoma protein (Rb), p53, p21

Negative Regulatory Molecule process

DNA Damage detected → p53 (activation) → p21 (production) → inhibits cyclin cdk → Cell cycle arrest → repair

EXAM Q: A cell experiences DNA damage. According to the pathway discussed in class, p53 activates p21. What is the expected result?

p21 inhibits cyclin-Cdk activity, causing cell-cycle arrest so the damage can be repaired.

Negative Regulatory Molecule process step 1

DNA Damage

Negative Regulatory Molecule process step 2 (after DNA Damage)

P53 (activation)

Negative Regulatory Molecule process step 3 (after p53 activation)

p21 (production)

Negative Regulatory Molecule process step 4 (after p21 production)

inhibits cyclin cdk

Negative Regulatory Molecule process step 5 (after cyclin cdk is inhibited)

Cell cycle arrest

Negative Regulatory Molecule process step 6 (after cell cycle arrest)

repair

Cancer (EXAM)

Covers many different diseases characterized by a loss of normal cell cycle control resulting in uncontrolled cell growth from checkpoint failure

Mutations in regulatory genes allow cells to _________ when they should stop

continue dividing

Multiple mutations can accumulate over successive divisions, eventually producing _________________

uncontrolled growth/tumors

Proto-oncogenes (normal “accelerator”) (EXAM)

Normal genes that code for positive cell cycle regulators

When normal genes mutate in certain ways, they become ______

oncogenes, potential to cause normal cell to lose ___

Tumor supressor genes (normal “brakes”)

Segments of DNA that code for negative regulator proteins. When activated, these can prevent uncontrolled division.

Cells with a ________ form of a negative regulator might not be able to stop the cell cycle if there is a problem

mutated

Tumor supressor = _____

Brake

EXAM Q: Match each term with the description that best fits

Cancer

A group of diseases characterized by loss of normal cell-cycle control and uncontrolled cell growth.

EXAM Q: Match each term with the description that best fits

Tumor Supressor Gene

A gene that codes for a negative regulator protein and acts like a cell-cycle brake.

EXAM Q: Match each term with the description that best fits

Oncogene

A proto-oncogene that has undergone certain mutations.

EXAM Q: Match each term with the description that best fits

Proto-Oncogene

A normal gene that codes for a positive cell-cycle regulator