Cell Death and Cancer SNC2D

First a bit more cell division… How do prokaryotes divide? Do all eukaryotes divide their cells using mitosis? Do all cells divide at the same speed? What factors affect mitosis? How do cells die?

1. Binary Fission ◦ Type of cell division used by prokaryotes (bacteria)

2. Budding Asexual reproduction in which a new organism develops from an outgrowth or bud on another one

3. Regeneration the process of restoration, and growth after damage

4. Fragmentation A form of asexual reproduction where an organism is split into fragments and each fragment develops into mature, fully grown individuals which are clones of the original organism

What other factors impact mitosis? ◦ Altitude, antibiotics… ◦ Can you think of any others?  Chemotherapy  Radiation  Sunlight

How do Cells die?

Apoptosis The material of the cell is recycled by the body.

Comparison

Apoptosis Videos Y8q_F3k Y8q_F3k TBM8tTo TBM8tTo

Cell Lifespans Cells do not live forever. They can only divide a certain number of times until they receive a message or instructions to die. Cell division is necessary for cells to be replaced after they die. In your body, 3 billion cells die every minute. We undergo cell division as part of regeneration, a process essential for repairing damaged tissue. Why do we age? ◦ Not entirely sure ◦ as cells die, they are not replaced or just not as quickly. This results in changes to the structure and function of major body systems.

What happens when damage to a cell impairs its ability to commit apoptosis and it divides and divides and divides?

Cancer Cancer = uncontrolled cell division Caused by changes in the genes controlling cell division loss of a cell’s ability to undergo apoptosis (“immortal”) ◦ On/off switch is broken ◦ Continually reproducing = Tumour

Cancer In small groups ◦ – Compare Normal Cells to Cancer Cells

Normal CellsCancer Cells Make exact copies of themselves through mitosis Make exact copies of themselves through mitosis Reproduce for about cell divisions Do not stop reproducing Stick together to form masses of cells as appropriate Do not stick to other cells Behave independently Self-destruct when too old or too damaged May move to another location of the body

Review: The cell cycle has four phases and controls cell division

Cell Cycle Checkpoints There are three checkpoints in the cell cycle ◦ G1-S transition ◦ G2-M transition ◦ Exit M phase transition Checkpoints are where the cell assesses whether conditions are favorable for cell division. When the environment is not favorable (for example, when the cell’s DNA is damaged), a protein called p53 can stop the cell cycle and cause the cell to die. When the proteins that regulate the cell cycle are mutated or absent, cells can divide controllably, leading to cancer.

Tumor suppressors and oncogenes Mutations in oncogenes and tumor suppressor genes can lead to cancer nts/nih1/cancer/activities/activity2_animati ons.htm nts/nih1/cancer/activities/activity2_animati ons.htm ◦ (animation #5)

Cell Cycle Checkpoints A cell should remain in interphase and not divide if… ◦ Signals from surrounding cells tell the cell not to divide ◦ There are not enough nutrients in the cell ◦ The DNA has not yet been replicated ◦ The DNA is damaged These checkpoints are regulated by special proteins like p53

Microscopic Appearance of Cancer Cells

Definitions Tumour: ◦ A mass of cells resulting from rapid cell growth

Benign: ◦ Tumours that stay confined in a small area, causing little damage Malignant: ◦ Dangerous tumours that break away and move to other areas of the body. Metastasize Spread of cancer

Causes of Cancer Mutation: ◦ Random changes that can occur when DNA is replicated Carcinogen: ◦ Any environmental factor that can cause a mutation

Videos on Cancer a2b5XI a2b5XI pYXwo pYXwo cancer-grows.html cancer-grows.html

ANDI – Inserted DNA Monkey with green glow protein from a jellyfish inserted into its DNA.

TgCat1 - Green Glow Cats These GM cats carry: ◦ Green fluorescent protein (GFP) gene ◦ and an extra monkey gene, called TRIMCyp, which protects rhesus macaques from infection by feline immunodeficiency virus or FIV – responsible for cat AIDS

Glow in the dark dog with an on/off switch! The switch is a chemical trigger Give the dog an antibiotic along with food, she’ll start to glow under UV light Tegon was cloned and in the process her genes were modified to instruct her cells to react to an antibiotic by glowing This research will help find cures to diseases (like Alzheimer's and Parkinson's) that are common to both dogs and humans Want one? She costs $3 million.

Curious Cloning… Random  In 2008 an American couple paid more than $150,000 to have their late pet dog cloned