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15 Cards in this Set
- Front
- Back
what is a polygenic trait or disease?
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a trait or disease caused by the impact of many different genes, each with a limited impact on the phenotype
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what are multifactorlal diseases?
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diseases caused by the interplay of multiple genes and multiple evironmental factors
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are polygenic traits normally quantitative or qualitative in nature?
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quantitative
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what is the threshold model of multifactorial disease?
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a model which states that some proportion of individuals above a certain threshold of genetic liability will develop the disease, especially if exposed to environmental triggers
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does the risk for mutifactorial diseases increase or decrease if more than one family member is affected?
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increases
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is the risk for a multifactorial disease necessarily higher if the expression of the disease is more severe in the proband?
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yes
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is the risk for multifactorial disease greater or less for the sibling of a proband of the less commonly affected sex?
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greater
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is the recurrence risk for the disease higher in first-degree or second-degree relatives?
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much higher in first-degree relatives
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is the frequency of multifactorial diseases higher within a family than in the general population?
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yes, it is higher within related individuals
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how can twins be used to see if a disease is passed genetically or not?
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if a disease is entirely genetic, 100% monozygotic twin pairs should be concordant for the disease, while only 50% of dizygotic twin pairs will be concordant
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other than family and twins, what is another indication of the genetic nature of a disease?
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if the disease is rare and passed in a Mendelian fashion
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why has the identification of genetic factors in IDDM involved analysis of affected sib pairs in families?
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if 2 siblings are both affected by a genetic disease, we would expect to see increased sharing of marker genes in the genomic region that contains a susceptibility gene
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what percentage of their genes do siblings share, on average? What proportion of marker polymorphisms would you expect to not be linked to a susceptibilty locus in siblings?
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50%; 50%
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if siblings share the same alleles for a marker polymorphism around 75%, of what is this evidence?
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marker is linked to a susceptibility locus
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in animal models, how must a diseases individual be mated to perform linkage analysis?
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diseases bred with normal to produce F1 then F1 backcrossed with normal to produce F2. Linkage analysis performed on recombined disease chromosome of F2
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