Autosomal Dominant Inheritance Flashcards
Heterozygous
Having a normal allele on one chromosome and a mutant allele on the other
Homozygous
Having mutant alleles on both chromosomes
Hemizygous
Having half the number of alleles
Dominant allele
An allele whose phenotype is detectable in a single dose or copy
Recessive allele
An allele whose phenotype is apparent only in the homozygous or hemizygous state
Pleiotrophy
Multiple phenotypic effects of a single gene
Locus
The position on a chromosome of a gene or other chromosome marker
Locus heterogeneity
Different genes can cause the same or similar phenotypes
Allelic heterogeneity
Population: different mutant alleles in one gene
Individuals: same/similar/different phenotype may be caused by different mutant alleles in one gene
Penetrance
Population: the proportion of people with a mutation who have any signs of the disease
Individuals: whether or not a gene is expressed
Expressivity
The range of symptoms; the condition is always penetrant but varies in severity
Molecular genetics acondroplasia
Point mutations in FGFR3
100% penetrance
Gain of function
Clinical features of achondroplasia
Short stature Rhizomelie Macrocephaly Characteristic facial features Hypotonia in children Normal intelligence Normal lifespan
Clinical Features Marfan
Tall, disproportionately long limbs
Chest deformity
Joint laxity
Scoliosis
Eyes: dislocation ocular lens, myopia, retinal detachment, early glaucoma
Heart: mitral valve prolapse, dilation of aortic root
Molecular genetics Marfan
FBN1 gene, 100s of mutations
Dominant negative effect
100% penetrant, variable expression
