BIO 302 Study Guide - Final Guide: Tumor Suppressor Gene, Thanatophoric Dysplasia, Cell Adhesion Molecule
Dominant genes:
• A gene will be expressed even if one copy of the gene is put forth
Recessive mutation
• Cystic Fibrosis: 1 in 25 people are a carrier
• 1/25 x 1/25 = 1/625 x4
• Recessive birth defects extreamley rare because both parents must be carrier
o Most birth defects are dominant
o 3 Cases of dominance:
1. Haploinsufficiency
a. Ex. Waardenburg syndrome; deafness due to one mutated copy of the
MITF transcription factor
2. Gain of function
. Loses regulation of a gene
a. Ex. signaling factor like FGF (limb patterning ) signal is not regulated; on all the time.
b. FGF receptor is activated all the time without ligand, “constitutively active”
c. Case: thanatophoric dysplasia (dwarfism): normal function of of FGF receptor → turn
down growth factors ← Too much down regulation of growth . Not evenly distributed, leads to
dwarfism
3. Dominant Negative
. Bad copy interferes with the function of the good copy.
a. Marfan’s syndrome( long limbs, long fingers; skeletal elements
extended, heart defects) Affects ECM protein “fibrillin” ( needed for heart
development and skeletal development)
2 kinds of genes that cause cancer
• Oncogenes
o Genes normally off in differentiated cells
▪ Ex. cell cycle control genes
• Tumor suppressor genes
o Genes normally on in differentiated cells
o Mutation would know them out
▪ Apoptosis regulation (cell death)
▪ DNA repair genes
▪ Cell adhesion molecules
Why are certain people more susceptible to cancer than others?
• Normal situation; two good copies of genes in every cell
• Cancer; two mutations in the same cell
o Inherit one mutant gene copy; retinoblastoma ; one bad copy of gene in every
cell, so mutation in any cell can lead to cancer
Who has the breast cancer gene BRCA1?
- both males and females
If BRCA1 is a gene that fixes mutations as they happen, would it be an oncogene or a tumor
suppressor?
- Tumor suppressor gene
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Document Summary
Dominant genes: a gene will be expressed even if one copy of the gene is put forth. Waardenburg syndrome; deafness due to one mutated copy of the. Ex. signaling factor like fgf (limb patterning ) signal is not regulated; on all the time. Fgf receptor is activated all the time without ligand, constitutively active . Case: thanatophoric dysplasia (dwarfism): normal function of of fgf receptor turn down growth factors too much down regulation of growth . Not evenly distributed, leads to dwarfism: dominant negative. Bad copy interferes with the function of the good copy. Marfan"s syndrome( long limbs, long fingers; skeletal elements extended, heart defects) affects ecm protein fibrillin ( needed for heart development and skeletal development) Why are certain people more susceptible to cancer than others: normal situation; two good copies of genes in every cell, cancer; two mutations in the same cell.
