Human Genetics chapter12 Flashcards
0
Q
Cancer two hit hypothesis
A
- Takes a long time to develop, mutations accumulate over time
- Individuals born with mutations will likely develop cancer sooner than wild types: inherited mutations require a specific mutation in the other copy or elsewhere for cancer to develop (loss of heterozygosity)
- Sporadic cases most common form of cancer
- Single dominant mutation or certain number of recessive mutations
1
Q
Cancer
A
- Genetic disease of the somatic cells
- Two properties: 1. Uncontrolled growth 2. Ability to metastasize
- Not all tumors are cancerous
- Benign: uncontrolled growth but does not metastasize
- Malignant: uncontrolled growth and metastasizes to other areas: starts in a single cell (all cells in tumor are clones of original cancer cell), develops after a cell accumulates a number of specific mutations over a long time
- Complex and deals with many different cells and tissue types
- Risk is age related, older more at risk: exposed to more carcinogens, background radiation
- Mutation to DNA is ultimate cause of cancer
2
Q
Metastasis
A
A process by which cells detach from the primary tumor and move to other sites,forming new malignant tumors in the body.
3
Q
Loss of heterozygosity(LOH)
A
In a cell, the loss of normal function in one allele of a gene where the other allele is already inactivated by mutation.
4
Q
Cell cycle regulation check points for cancer
A
- G1/S: point in G1 just before the cell begins to replicate in S phase
- G2/M: point prior to transition from G2 to M
5
Q
Tumor-suppressor genes
A
- Turns off or decreases the rate of cell division
- Gene products act at either the G1/S or G2/M control point to inhibit cell division
- When mutated, these genes no longer suppress tumor cell growth
- Cells pass through checkpoints and divide in uncontrolled manner
6
Q
Proto-oncogenes
A
- Turn on or increase the rate of cell division
- Encodes proteins important for cell division
- Cells grow and divide when active, stop when turned off
- Mutations switch these on permanently or overproduce their gene products
- Cells are stimulated to divide in uncontrolled manner
- Mutant forms are called oncogenes (permanently switched on)
- Normally switched off when cell division stops
7
Q
Oncogenes
A
Genes that induce or continue uncontrolled cell proliferation.
8
Q
Signal transduction
A
- The transmission of signals from the plasma membrane to the nucleus to alter gene expression
- Ras proto-oncogene encodes for these proteins
- Normal Ras proteins cycles between on or off depending on extra cellular signals
9
Q
Retinoblastoma
A
- A malignant tumor of the eye that affects young children
- Caused by a mutation in a tumor-suppressor gene
- Familial retinoblastoma: individuals who inherit one mutant copy of RB1 are likely to develop retinoblastoma (autosomal dominant), may result in other cancers via LOH if mutation to the normal copy occurs because it’s carried in all their somatic cells
- Sporadic retinoblastoma is very rare, develop retinal tumors but not at risk of developing tumors elsewhere
10
Q
Cancer shared properties
A
- Higher than normal mutation rate
- Abnormalities of chromosome structure
- One or more forms of genetic instability: aneuploidy in chromosomes, duplications, deletions, etc.
- Related to loss of the ability to repair DNA damage in cancer cells
11
Q
BRCA1 and BRCA2
A
- Mutations result in a predisposition to breast cancer
- These are DNA repair genes
- Each gene is highly expressed at the G1/S boundary
- BRCA 1/2 protein activated when DNA is damaged
- Cells lacking BRCA 1/2 accumulate mutations
12
Q
Gatekeeper genes
Examples
A
- Control the cell cycle
- Mutations to these genes open the gates to uncontrolled cell division
- Ex. Tumor suppressor genes and proto-oncogenes
13
Q
Caretaker genes
A
- Encode proteins that maintain the integrity of the genome
- DNA repair genes like BRCA1/2
- Mutation doesn’t directly lead to cancer, but mutation rate of genes increase (including gatekeepers)
14
Q
Familial adenomatous polyposis (FAP)
A
An autosomal dominant trait resulting in the development of polyps and benign growths in the colon. Polyps often develope into malignant growths and cause cancer of the colon and/or rectum.
