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37 Cards in this Set
- Front
- Back
Define Segregation
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The transmission of genes from generation to generation.
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What is cosegregation?
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The transmission of more than one gene together.
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What is linkage?
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The increased likelihood of two genes being transmitted together because they're close on the same chromosome.
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What are 2 things that determine the likelihood of linkage?
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-Recombination
-Distance between loci |
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What are the 2 configurations of alleles in an individual that is heterozygous for 2 autosomal recessive genes that are linked?
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AB/ab (cis)
or Ab/aB (trans) |
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What would be the frequency of gametes produced by this individual if they are cis?
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50% AB
50% ab |
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What would be the frequency of gametes produced by this individual if they are trans?
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50% Ab
50% aB |
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What happens to gene transmission of 2 loci that are farther than 50 cM apart?
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They get transmitted to offspring gametes randomly and independently.
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What happens to gene transmission of 2 loci that are less than 50 cM apart?
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They get transmitted together more frequently than predicted by chance.
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What is a typical LOD score that indicates likely linkage?
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+3
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What is a LOD score that is against linkage?
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-2
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What allows visualization of a linked marker?
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If it shows up in consanguinous marriage children, but not in normal marriage's children.
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What is the most common lethal genetic disease of childhood? How many births is it seen in?
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Cystic fibrosis - in 1/1000 live births
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What type of inheritance is Cystic fibrosis?
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Autosomal recessive
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What method was used to identify the CF gene?
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Positional cloning
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What are the 4 tissues in which only gene CFTR is abnormal in all of them?
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-Pancreas
-Airways -Sweat glands -Liver |
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What results from Cystic fibrosis in the lungs?
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COPD - increased mucus
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What does CFTR stand for?
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Cystic fibrosis transmembrane conductance regulator
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What is the conductance regulator?
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A chloride channel that is responsible for salt balance.
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Why is it important to know that Positional cloning was used to identify the CFTR gene?
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Because it was the first disease gene identified via this technique.
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How many known mutations cause cystic fibrosis?
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Over 120
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What type of gene defect causes Hungtington's disease?
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Polyglutamine tracts - accumulations of Glutamine.
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What type of inheritance is Huntington's disease?
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Autosomal dominant
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What type of genetic analysis localized the Huntington disease gene to the tip of Ch' 4?(in 1983)
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Linkage analysis
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How was the huntingtin disease gene itself identified in 1993?
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By exon trapping
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What category are polyQ diseases like Huntington's disease an example of?
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Triplet expansion diseases
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What are All triplet expansion diseases? What do they all affect?
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-Dominant
-All affect the brain |
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What are 4 triplet expansion diseases?
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-Huntington's
-Fragile X -Kennedy syndrome -Myotonic dystrophy |
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What can be defined for each triplet expansion disease?
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A threshold of # of repeats over which the symptoms appear and degeneration ensues.
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What do we call disorders like cystic fibrosis and PolyQ diseases, where we can identify the gene itself?
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Monogenic disorders
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How are polygenic disorders different from monogenic?
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They are affected by
-multiple genes -environmental factors -lifesyle |
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What problems result for genetic analysis in polygenic disorders?
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-Individual genes don't have a huge impact - and for those genes that do, huge families are needed for studies.
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Why do multi-generational pedigrees need to be recruited for genetic analysis of polygenic disorders?
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Because most of these disorders develop later in adulthood.
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When Linkage analysis is used for studying polygenic diseases, what does it result in identifying?
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Quantitative trait loci - QTL
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What is a QTL?
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A large region of DNA.
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What is linkage analysis useful for?
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Identifying loci that contribute to both monogenic or polygenic disorders
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What is linkage analysis MOST powerful for identifying?
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Genes with large phenotypic effets - monogenic.
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