Genetics Flashcards
Do all mutations alter proteins?
No
Do all mutations affect phenotype?
No
Are loss of function mutations usually dominant or recessive?
recessive
What is haploinsufficiency?
reduced activity from lof mutation is not sufficient, causing the phenotype to be dominant
What is a gain of function mutation? Is it usually dominant or recessive?
dominant; novel action is gained from mutation EX: Huntington’s disease increases protein aggregation and causes cell toxicity
What is a dominant negative mutation?
abnormal function interferes with normal allele EX: collagen mutation in osteogenesis imperfecta
What is a transition mutation?
AT –> GC
What is a transversion mutation?
CG –> GC
What is a missence mutation?
changes AA to one with dissimilar biochemical properties
What is a nonsense mutation?
early stop codon
What is a neutral mutation?
changes AA to one with similar biochemical properties
What is a silent mutation?
bp change which does not change AA
What is a frameshift mutation?
changes rule of 3 and alters entire protein sequence
What is the difference between genetic heterogeneity and pleitropy?
genetic heterogeneity: many alleles can give rise to same phenotype
pleitropy: single allele can give rise to several phenotypes
What is the classic example of allelic heterogeneity?
Cystic Fibrosis
What is locus heterogeneity?
phenotype caused by mutations in genes at different chromosomal loci
What is the classic example of locus heterogeneity?
retinitis pigmentosa
Mutations in what typically leads to diseases of the connective tissues?
collagen or elastin
What is the clinical presentation of Ehlers-Danlos Syndrome (EDS)?
class of 10 disorders with joint flexibility problems; loose joints, stretchy skin
What is the clinical presentation of Epidermolysis Bullosa (EB)?
skin blisters and tearing
What is the clinical presentation of Marfan Syndrome?
long, tall, and fragile (fibrilin (elastin) mutation)
What is the clinical presentation of Osteogenesis Imperfecta?
brittle bone disease; blue sclera
What is the role of the FBN1 gene in Marfan Syndrome?
part of cell signaling pathway which increases TGF-beta signaling; weakend heart valves, lungs, aorta
What are the implications for lack of lysine in the diet versus lack of tryptophan in regards to collagen formation?
tryptophan never integrates into collagen so it is less deleterious to not have it in one’s diet
What is a sarcoma?
malignant tumor of mesenchymal origin
What is a carcinoma?
malignant tumor of epithelial origin
What are the two stages of acquiring cancer?
1) activatino of an oncogene
2) destruction of tumor suppressor gene
What is the most common virally-induced cancer?
HPV leads to cervical cancer
Most cells of the body are in which phase of the cell cycle?
G1 phase
Where is the cycle check in the cell cycle?
G1 to S phase
G2 to Mitosis
oncogenes destroy these “stop signs”
When is DNA doubled in the cell cycle?
S phase
What turn on and off the cell cycle?
cyclin-dependent kinase (cdk)
What is the most important tumor suppressor gene?
p53
What is retinoblastoma?
Ch13, RB1 gene
Can be inherited + acquired 2nd mutation
or both acquired
What is the “two-hit hypothesis”?
tumor suppressor genes cause cancer when both copies of the allele are mutated
Which cancer mutation would be more probable to inherit, proto-oncogene or tumor suppressor gene?
tumor suppressor gene
How does the Philadelphia chromosome cause cancer?
constitutively activate a proto-oncogene with a promoter from another onco-gene through translocation
