Chapter 5 (Part 2) Flashcards
the cell cycle is controlled by…
checkpoints
what is apoptosis?
programmed cell death
mutations are either _______ or ________
repaired or undergo apoptosis
3 principal checkpoints control the cycle in eukaryotes
G1, G2, and M checkpoints
G1 checkpoint
- Determines whether the cell should enter S phase for DNA replication and cell division
- Some cells never pass this point and are said to be in G0
G2 checkpoint
- Determine if mutations occurred in DNA replication
- Repair enzymes available to correct mutations.
M checkpoint
Occurs during metaphase and determines whether mitosis should proceed. Triggers exit from M phase
and entry into G1 phase
Cancer results from…
mutated cells growing unregulated by growth checkpoints
oncology
the study of cancer
the result of cancer is a growing cluster of cells is called a
tumour
Benign tumours
surrounded by a smooth layer of cells and do not spread to other areas
Malignant tumours
have irregular cell borders, are not encapsulated, and are invasive. cells leave and spread to other areas forming new tumours
new tumours are called
metastases ( or secondary tumours)
what are the two general classes of genes that are usually involved in cancer?
Proto-oncogenes, tumour-suppressor genes
Proto-oncogenes
*These genes encode proteins that stimulate the cell cycle.
*Mutations to these genes can cause cells to divide excessively.
*When mutated, they are called oncogenes.
tumour-suppressor genes
- Encode proteins that normally arrest the cell cycle (at the three checkpoints).
- When mutated, these genes are not able to control rate of cell division.
- p53 is the most famous example of this gene type
cancer may develop if any of these types of genes are mutated
- Genes regulating the cell cycle: such as proto-oncogenes and tumor-suppressor genes
- DNA repair enzymes (→ more mutations)
- Genes involved in apoptosis (→ cancer cells live on)
- Genes that regulate the immune response (→ cancer cells escape NK cells)
- Genes that increase angiogenesis (→ more nutrients for growth of the tumour)
cancer can result from…
damaged genes failing to control cell division
the tumour suppressor gene p53 affects what checkpoint?
G1
- usually detects abnormal DNA
- can stop the cycle and recruit DNA repair enzymes.
- if cannot be fixed, cell goes into apoptosis.
if mutation is detected, tumour-suppressor gene can…
stop the cell cycle and direct repair enzymes to the mutation. If that fails, they can trigger apoptosis
What does the immune system do when a mutated cell continues to divide unregulated?
the immune system has natural killer cells and cytotoxic T-cells that can destroy cancerous cells.
less exposure to mutagens =
less mutations to take care of which also means less chance for cancer.
cancer is caused by
damaged genes in stomatic tissue that fail to properly control the cell cycle
cause or orgin of damaged genes
- Familial or Inherited Genetic Mutations (5-10%)
- Genetic Mutations from Environmental Factors (90-95%)
