Genetics Flashcards
mendelian
trait that is attributable to a single gene
autosomal recessive inheritance
one bad allele from each parent, affected siblings only, even sex ration, usually skips a generation
X-linked recessive
multiple affected generation, no male to male transmission, skewed sex ratio because males only need one bad allele
autosomal dominant
multiple affected in multiple generations, even sex ratio, 1:1 affected
multifactorial inheritance
deleterious mutations of a number of nuclear genes, each having a small effect
insufficient gene dosage example
Waardenburg syndrome I; mutant allele in PAX3 results in product of normal allele not reaching threshold for normal phenotype (haploinsufficiency)
symptoms of Waardenburg syndrome
deafness, ocular hypertelorism, pigmentation abnormalities
excessive gene dosage example
Charcot-Marie-tooth type 2 which is duplication of PMP22 allele (copy number variation)
Charcot-Marie-Tooth disease
destabilizes myelin sheath resulting in nerve death
increased protein activity example
achondroplasia; activation of FGFR3 even in absence of ligand, inhibiting proliferation and differentiation of growth plate chondrocytes
example of gene being present in right place
ectopic expression of HOXA2 results in odd shaped ear
example of new protein function
alpha1-antitrypsin can no longer inhibit elastase because of a point mutation
example of gene product becoming toxic
huntington disease; expansion of CAG repeats results in an increase in glutamine residue within huntingtin protein resulting in accumulation of abnormal protein and brain cell death
example of dominant negative mutation
osteogenesis imperfecta type II; alpha2 procallogen mutation also affects the alpha1 procollagen molecules
mechanisms of dominant inheritance
- insufficient dosage
- excess dosage
- incorrect timing or place of expression
- increased protein activity
- new protein function
- alteration to toxic protein
- dominant-negative mutations
