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13 Cards in this Set
- Front
- Back
- 3rd side (hint)
Codominence |
Both alleles contribute to heterozygote phenotype eg. blood group, A1AT deficiency |
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Variable expressivity |
Phenotype varies among individuals with same genotype eg. Neurofibromatosis type I |
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Incomplete penetrance |
Not all individuals with mutant genotype show mutant phenotype eg. BRCA1 |
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Pleiotropy |
One gene contributes to multiple phenotypic effects eg. Untreated PKU can manifest with light skin, intellect disability, musty body odor etc. |
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Anticipation |
Increased severity or earlier onset of disease with succeeding generations. Trinucleotide repeat diseases eg. Huntingtons |
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Loss of heterozygosity |
Mutation of tumour suppressor gene requires deletion/mutation of complementary allele before cancer develops. "two-hit hypothesis" eg. Retinoblastoma |
"two hit hypothesis" |
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Dominant negative mutation |
Heterozygote produces non-functional protein that also prevents normal gene product from functioning |
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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 family. |
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Mosaicism |
Presence of enetically distinct cell lines in same individual. Somatic = mutation from mitotic errors after fertilisation. Gonadal = mutation only in egg or sperm cells eg. McCune-Albright syndrome |
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Locus heterogeneity |
Mutations at different loci can produce similar phenotype eg. Albinism |
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Allelic heterogeneity |
Different mutations in same locus produce same phenotype eg. B-thalassaemia |
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Imprinting |
At same loci, only one allele active (other is imprinted/inactivated by methylation). Deletion of active allele = disease Prader-Willi: maternal (chr 15) AngelMan: paternal (chr 15) |
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Uniparental disomy (heterodisomy vs. isodisomy) |
Two copies of chromosome from one parent, nil from other. Heterodisomy: non-identical chromosomes (meiosis I error) Isodisomy: identical chromosomes (meiosis II error or postzygotic duplication) eg. recessive disorder seen when only one parent is carrier. Prader-Willi/AngelMan syndromes occasionally result from two imprinted genes. |
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