Flashcards - Genetics
Chromosome 3
von Hippel-Lindau disease, renal cell carcinoma
Chromosome 4
ADPKD with PKD2 defect, Huntington disease
Chromosome 5
Cri-du-chat syndrome, familial adenomatous polyposis
Chromosome 7
Williams syndrome, cystic fibrosis
Chromosome 9
Friedreich ataxia (GAA)
Chromosome 11
Wilms tumor
Chromosome 13
Patau syndrome, Wilson disease
Chromosome 15
Prader-Willi (paternal deletion) syndrome, Angelman (maternal deletion) syndrome
Chromosome 16
ADPKD with PKD1 defect
Chromosome 17
Neurofibromatosis type 1
Chromosome 18
Edwards syndrome
Chromosome 21
Down syndrome
Chromosome 22
Neurofibromatosis type 2, DiGeorge syndrome (22q11)
Chromosome X
Fragile X syndrome, X-linked agammaglobulinemia, Klinefelter syndrome (XXY)
Codominance
Both alleles contribute to the phenotype of the heterozygote.
Variable expressivity
Phenotype varies among individuals with same genotype.
Incomplete penetrance
Not all individuals with a mutant genotype show the mutant phenotype.
Pleiotropy
One gene contributes to multiple phenotypic effects.
Anticipation
Increased severity or earlier onset of disease in succeeding generations.
Loss of heterozygosity
If a patient inherits or develops a mutation in a tumor suppressor gene, the complementary allele must be deleted/mutated before cancer develops. This is not true of oncogenes.
Dominant negative mutation
Exerts a dominant effect. A heterozygote produces a nonfunctional altered protein that also prevents the normal gene product from functioning.
Linkage disequilibrium
Tendency for certain alleles at 2 linked loci to occur together more or less often than expected by chance. Measured in
a population, not in a family, and often varies in different populations.
Mosaicism
Presence of genetically distinct cell lines in the same individual.
Somatic mosaicism—mutation arises from mitotic errors after fertilization and propagates through multiple tissues or organs.
Gonadal mosaicism—mutation only in egg or sperm cells.
Locus heterogeneity
Mutations at different loci can produce a similar phenotype.
Allelic heterogeneity
Different mutations in the same locus produce the same phenotype.
Heteroplasmy
Presence of both normal and mutated mtDNA, resulting in variable expression in mitochondrially inherited disease.
Uniparental disomy
Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent. Heterodisomy (heterozygous) indicates a meiosis I error. Isodisomy (homozygous) indicates a meiosis II error or postzygotic chromosomal duplication of one of a pair of chromosomes, and loss of the other of the original pair.
Menkes disease
XL - defective ATP7A - decreased lysyl oxidase activity - kinky brittle hair, growth retardation, hypotonia