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22 Cards in this Set
- Front
- Back
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Define: Disease gene is identified through knowledge of the function of the protein product. Extremely successful in some cases such as hemoglobinopathies.
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Functional cloning
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Define: Identifying disease genes based on their locations in the genome without any prior knowledge of the biochemical defect.
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Positional cloning
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Describe the two main steps of the positional cloning.
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1. Approximate location of the region responsible for the diseas is define.
2. Once the gene location has been mapped to a short interval, molecular techniques are used to ID it specifically. |
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Define: Coninheritance of genes located closely on the same chromosome.
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Linkage
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Define: The frequency of recomgination between two linke loci.
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Recombination fraction
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Define: The log of the odds.
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LOD
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What does LOD compare?
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The liklihood (or probability) of obtaining the particular datset if the loci are linked, to the likelihood of obtaining the same data set if the loci are unlinked.
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Define: Recombination frequency between two loci expressed in %.
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Genetic distance
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Define: Containing two different alleles from two different parents.
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Recombinant
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Define: The relative position of loci along a chromosme, as determined by genetic linkage analysis.
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Genetic map
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Define: A set of linked polymorphic alleles.
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Haplotype
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Approximately what percentage of the human genome encodes protein?
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1.5%
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About how many protein-coding genes are present in the human genome?
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30,000
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What is the ratio of polymorphism in the 98% of genes which do not code for protein?
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1 in 500 to 1 in 1000
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Define: An Actual polymorphism that distinguishes between two or more gene alleles.
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Genetic marker
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Name 4 types of polymorphism.
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VNTR (Variable numbers of tandem repeats)
SNPs (Single nucleotide polymorphisms) RFLP (Restriction fragment Length polymorphisms) Microsattelites (SSRs or simple sequence repeats) |
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Explain the four step process for mapping disease genes by linkage analysis.
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1. Enroll a sufficient number of affected families
2. Determine the disease status of each family member 3. Determined genotpyes at a set of polymorphic markers across the genome 5. Analyze the gene responsible for the disease phenotype for linkage to each of the polymorphic markers. |
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When does linkage disequilibrium occur
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When there has not been sufficient time for recombination to shuffle the haplotypes and the specific alleles remain linked.
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Define: Modern descendant sof a relatively few individuals who left one area to settle another. Often have significantly higher incidences of some diseases. Have greater averall genetic homogeneity in these opulations makes it much more likely that individuals with the same disease have mutations in the same susceptibility genes.
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Founder populations
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Why are founder populations useful in identifying genes for complex traits?
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The genetic homogeneity makes it more likelyt that identified genetic differences between patient and control groups are significant and not false positives. These factors help reduce the signal-to-noise problem in gene discovery studies.
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Define: A catalog of SNPs and other genetic variants (alleles) that occur in human beins. It describes twhat these vairants are, where they occur in our DNA, and how they are distributed among people within populations and among populations in different parts of the world.
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HapMap
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What is the significance of the HapMap project?
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It identifies the most common SNP associations within chromosomes. It is designed to give other researchers information that can be used in association studies. Data generated by the project can be downloaded with minimal constraints.
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