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22 Cards in this Set
- Front
- Back
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Null Mutation
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LOSS OF FUNCTION
•Null mutation – AR o Reduced or no function, 50% function is sufficient for carriers |
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Dosage Effect
-& two examples |
LOSS OF FUNCTION
•Dosage effect – AR & AD o One allele = AD, called incomplete dominance or haploinsufficiency o Two alleles = AR, severe disease o Example: familial hypercholesterolemia -One allele is somewhat elevated cholesterol -Two alleles is very elevated cholesterol levels & cholesterol deposits in eye o Example: potassium voltage-gated channel - One allele is long QT syndrome - Two alleles is deafness & long QT syndrome |
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Dominant Negative
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LOSS OF FUNCTION
•Dominant negative – AD o Mutant protein interferes with function of normal protein |
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Gain of Function Mutation
-& two examples |
• AD, requires very specific
mutation •Example: Achondroplasia o Mutation causes protein to have new function that leads to short bones •Example: Huntington’s Disease |
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Benefits vs challenges of DNA testing
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•Benefits:
Confirmation of diagnosis, presymptomatic diagnosis, genotype-phenotype correlation •Challenges: variable expression, heterogeneity, allelic disorders, non-paternity |
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Karyotype analysis detects what?
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Karyotype analysis – detects deletions, duplications, translocations
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FISH detects what?
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FISH – detects known deletions/duplications
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Methylation Specific RT-PCR–for Prader Willi/Angelman syndromes does what?
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Can determine whether imprinted regions are presented in appropriate number
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CHIP technology?
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CHIP technology – looks for insertions & deletions
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Direct sequencing does what?
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look for disease causing mutations
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Short Tandem Repeat Polymorphisms tell you what?
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paternity test
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Multiple Ligation-dependent Probe Amplification can do what?
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can look for duplications/deletions in exons
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Population Screening does what?
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•Presymptomatic detection – newborn screen state mandated
•Reproductive decision making – different diseases & alleles tend to be carried by different populations of individuals |
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-Aneuploidy
-Polyploidy -Reciprocal -Robertsonian -Inversion -Ring Chromosome -Isochromosome |
-Aneuploidy – off by a few (monosomy, trisomy, tetrasomy)
-Polyploidy – off by a whole set (triploidy, tetraploidy) -Reciprocal– balanced translocation -Robertsonian – clinically no implications -Inversion: -pericentric (involves centromere) -paracentric (doesn’t involve centromere) -Ring Chromosome – will be written like 46,XX,r22 -Isochromosome – divide wrong at meiosis (p arms go together, q arms go together &whoever gets centromere wins) -written 46, X, i(Xq); Turner Variant |
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Down Syndrome
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Trisomy 21
•Clinical Features: flat facial profile, fingers curling in, upslanting eyes, single palmar crease •Associated Findings: mental retardation, congenital heart disease, GI abnormalities, atlantoaxial instability, leukemia, strabismus (eye abnormality), thyroid abnormalities |
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Edwards Syndrome
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Trisomy 18
•Clinical Findings: fingers don’t straighten out, facial abnormalities, low-set ears, rocker bottom feet |
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Patau Syndrome
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Trisomy 13
•Clinical findings: Oral-facial clefts, polydactyly (extra digit of hands/feet), scalp defets |
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Cri-du-chat syndrome
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-deletion of terminal end of 5p chromsome
•Diagnosed by cat like cry, dysmorphic face features, mental retardation |
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Turner Syndrome
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•One X chromosome (45,X), usually miscarry
•Increased swelling/edema, thick/webbed neck, puffy feet & hands, NORMAL INTELLIGENCE, short stature treated with growth hormone |
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Klinefelter Syndrome
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-XXY (XXXXXXY)
•Affected children have learning disabilities, relatively tall, testosterone therapy essential |
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-XXX
-XYY |
XXX – decreased IQ, speech delay
XYY – decreased IQ, impulsivity, emotional behavior |
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Contiguous gene syndromes
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•Clinical syndrome defined before genetic basis known, caused by submicroscopic deletion
oUsually need FISH to diagnose the syndrome •Examples: oPrader Willi oAngelman oVelo-Cardio- Facial/DiGeorge oWilliams oMiller-Dieker (lissencephaly) |
