Cell Cycle and Cancer Basics (2025)

Tumor suppressor gene

Class of genes whose protein products work to stop the cell cycle at checkpoints. Function as the brakes for the cell cycle.

Must mutate both genes to cause cancer

G1, S, G2, M (Mitosis or Meiosis)

4 Stages of the cell cycle

Mutations

Changes in DNA

DNA Repair Proteins

Remove and Replace damaged Nucleotides (can do this when cell is in cell cycle or G0)

Non-disjunction

In meiosis when segregation of chromosomes does not occur properly and one germ cell receives one extra chromosome and the other one is missing.

"Healthy" Cell types that are in the cell cycle as an "adult"

Skin cells (include hair cells)

Cells of gastrointestinal tract

Blood cells (both red and white)

These cells are most commonly affected by radiation and chemotherapies because they are in the cell cycle.

Embryogenesis

During this process, cells become more and more differentiated and specialized.

Differentiation (g0)

Cell exits the cell cycle to become a cell with a job. .(Also called g0)

Tumor

A mass (pile) of cells (Happen as a result of too much cell cycle)

Proto-oncogenes

Class of genes whose protein products work to make the cell cycle go forward. Works as gas pedal of cell cycle.

Only need to mutate one copy in cancer

Are called porto-oncogenes when healthy. When mutate them they are called oncogenes.

Apoptosis

Programmed Cell Death (Cell Suicide)

Cell Cycle

4 phase process where cell grows, duplicates and divides to make 2 daughter cells (or 4 in meiosis)

Checkpoints

Cell stops at these during the cell cycle to make sure the previous stage was completed correctly. (TSG)

DNA Replication

From one strand to two strands of DNA- Happens during S phase of Cell Cycle (DNA Polymerase)

mitosis or meiosis

Cell division- Last stage of Cell Cycle

Mitosis

cell division in which the cell divides into two daughter cells containing the same number of chromosomes as parent cell

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

crossing over

Exchange of genetic material between homologous chromosomes in meiosis. (Largest source of genetic diversity in life)

Differentiated Cell

Can only be in g0 or the cell cycle (Almost all "adult" cells)

Embryogenesis and wound repair

Two reasons a "healthy" adult cell would be in the cell cycle

Wound Repair

Cells undergo the cell cycle to replace missing cells

Embryogensis

Development from Zygote to birth

stem cells

cells that have the ability to divide without limit AND give rise to more specialized cells

Cancer

Uncontrolled Cell Growth and Division

mutations

Anything that causes these will increase your risk of cancer

Carcinogens

Cancer causing chemicals (Because cause mutations)

tumor suppressor genes

Class of proteins that repair DNA (Only one function of this class of proteins)

tumor suppressor genes

One "job" of this class of proteins is to trigger apoptosis when necessary because too much DNA damage

Chemotherapy

Chemicals that aim to kill cells that are in the cell cycle.