Term
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Definition
•All or part of the germline of an individual contains an allele not present in the somatic cells.
Recurrence risk for future offspring of the mosaic parent is increased |
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Term
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Definition
- the expression of the disease phenotype by less than 100% of the individuals who possess the disease-causing genotype.
ex. Retinoblastoma (90% penetrance)
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Term
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Definition
•Clinical expression of some genetic diseases does not occur in infancy and affected individuals are not diagnosed until later in life.
ex Huntington's Disease
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Term
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Definition
•Expression of the phenotype varies greatly in severity in some disorders.
•If the phenotype is expressed to any degree the disorder is penetrant.
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Term
Factors that influence Variable Expression |
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Definition
- enviornmental factors
- modifier genes
- allelic heterogeneity
- locus heterogeneity |
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Term
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Definition
-different alleles (mutations) at a specific locus can produce varying expression of a disease |
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Term
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Definition
• A single disease phenotype caused by mutations at different loci in different families
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Term
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Definition
•Traits that are expressed in only one of the sexes due to gender specific differences, such as anatomical differences.
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Term
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Definition
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•Progressively earlier or more severe expression of a disease in the most recent generations
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–Expansion of DNA repeats is the cause of anticipation in some diseases.
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Term
Affected females with an X-linked recessive disorder:
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Definition
•Manifesting heterozygote: Skewed inactivation with greater representation of the mutant allele in the active X chromosomes
•About 5% of female carriers of hemophilia A have factor VIII levels low enough to be considered mild hemophiliacs
•Turner syndrome: female with only one X chromosome - 45,X.
•Translocations or deletions of the X chromosome
•Homozygous female: father affected and mother a carrier
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