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24 Cards in this Set

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  • Back
Fragile X incidence
1/4000 males, 1/8000 females
Fragile X inheritance
X-linked with anticipation due to trinucleotide repeat expansion of CGG in the first exon of FMR1 gene
Fragile X mutation status
– normal (~5 to ~44) - intermediate (~45 to ~58) - premutation (~59 to ~200) - full mutation (over 200 and highly methylated)
Fragile X labs
– Southern blot detects presence of full and pre-mutations, approximation of repeat number, and methylation status
- PCR yields accurate estimates of normal and small pre-mutation alleles
What can premutation carries of fragile X develop
- Premutation females may develop premature ovarian failure
- premutation males may develop an ataxia/tremor syndrome
Huntington’s Incidence
- 3-7/100,000 in those of Western European descent
– less in Asia and Africa
Huntington’s genetics
- Expansion of a CAG triplet repeat within the HD gene on chromosome 4p
- normal (< 26)
- intermediate-sized alleles (27-35, ok but can pass to kids)
- reduced penetrance alleles (36-39, sx in some)
- adult onset (40-59)
- juvenile onset (above 60)
Huntington’s labs
PCR detects repeat number
How is CAG different from CGG
- smaller expansions
– Methylation is not involved in expression of the genes
– expansions larger when expanded allele inherited from father
– 5% of Rx (Warfarin, Phenytoin, Glipizide)
– poor metabolizers are 2C9*2 and 2C9*3
– 25% of Rx (TCAs, SSRIs, beta blockers, antipsychotics)
– poor metabolizers are 2D6*3, *4, *5del, *10, *17 – ultra rapid metabolizers are *2XN
– 15% of Rx (Antiarrhythmics, SSRIs, Diazepam)
– poor metabolizers are *2, *3
Poor metabolizers
– from 2 inactive gene copies (alleles)
– drug rxns are Adverse events/ toxicity
– Poor response to prodrug
Intermediate metabolizers
– from 2 alleles with reduced activity/ 1 inactive allele
– drug rxns are some adverse events
– Reduced response to prodrug
Extensive metabolizers
– from 2 normal alleles
– drug rxns are expected response
– Expected response to prodrug
Ultrarapid metabolizers
– from more than 2 copies of gene (duplication)
– Poor response to drugs
– Adverse effects in response to prodrug
Psychiatric drugs CYPs
2D6 and 2C19
2C9 and warfarin
– Metabolizes >90% of S-Warfarin
– 2C9*3 in 15% W and <5% A, B and reduces enzyme activity by 50%
– 2C9*2 in 10% Cauc and <5% A, B and reduces enzyme activity by 15%
– Variant alleles need lower doses, more time to stabilize INR, higher risk of bleeding
– enzyme activity is way down w/ spontaneous bleeding (VKCFD2)
– introns means decreased warfarin binding and warfarin resistance
– SNP’s can increase or decrease enzyme activity
DMD incidence
- Most common childhood muscular dystrophy
- 1/3500 male births
- female carriers estimated to be 1/1500
DMD inheritance
- X-linked recessive, gene on Xp21
- 2/3 of mothers are carriers, 1/3 are new mutations
- a genetic lethal as affected males rarely, if ever, reproduce
DMD mutations
- Allelic heterogeneity
– dystrophin gene large (2300 kb)
- 70% of w/ DMD and 85% w/ BMD have a deletion or duplication
- detectable by PCR or Southern blotting
– 30% w/ DMD have small insertion, deletion, point mutation, or splice site mutation
- detectable by mutation scanning and/or sequencing
What are DMD carriers at greater risk for?
LV dilation and cardiomyopathy
for MCAD deficiency, what do you look for on MS/MS
look for C8 and C10