Genetic Terms Flashcards
Codominance
Both alleles contribute to the phenotype of the heterozygote (ex: Blood groups AB)
Variable expressivity
People with the same genotypes have different phenotypes
Incomplete penetrance (calculate risk of expressing phenotype)
Not all individuals with disease exhibit classic phenotypes of the disease.
% penetrance x probability of inheritance = risk of expressing phenotype
Pleiotropy
One gene contributes to multiple phenotypes (PKU manifests as light skin, intellectual disability, and musty body odor)
Anticipation
Increased severity or earlier onset (more severe outcome) in next generations
Loss of heterozygosity
If a mutation is present in a tumor suppressor gene, the wild type allele must be deleted/mutated before cancer can develop. “Two-hit hypothesis”
Epistasis
The allele of one gene affects the phenotype expression in another gene
Aneuploidy (and due to what?)
An abnormal number of chromosomes due to chromosomal nondisjunction during mitosis/meiosis
Dominant negative mutation
A heterozygote produces a nonfunctional mutant protein that also prevents the wild type protein from functioning. Exerts a dominant effect.
Linkage disequilibrium
Tendency of alleles to occur in close proximity within the same chromosome more/less often than expected. Measured throughout populations
Mosaicism
Genetically different cells in the same tissues/organs
Somatic: mutation from mitotic errors
Germline: mutation from egg/sperm cells
Locus heterogeneity
Mutations at different loci resulting in the same disease
Allelic heterogeneity
Same locus, different mutations, result in the same disease
Heteroplasmy
Normal and mutated mtDNA resulting in variable expression in mitochondrial disease. To distinguish between all the other heteros remember heteroplasMy = mitochondria
Uniparental disomy
Offspring receives 2 copies of a chromosome from one parent and NONE from the other parent.
Heterodisomy (one I) = heterozygous meiosis I error
Isodisomy (two I’s) = homozygous meiosis II error or postzygotic chromosomal duplication of one pair of chromosome and complete loss of the other original pair