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Clinical genetics
MHG
23
Medical
Graduate
10/26/2011

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Cards

Term
Advanced maternal age
Definition
-35
-increased risk of cytogenetic mutations such as Down syndrome
Term
Advanced paternal age
Definition
-35
-increased risk of single locus mutations such as achondroplasia, neurofibromatosis (usually dominant)
Term
Haploinsufficiency
Definition
Still making correct protein - just not enough to maintain full functionality
Term
Oligonucleotide ligation assay (OLA)
Definition
-used to test for CF
-uses PCR - mutant probe is larger
-signal tells whether normal, heterozygous, or mutant homozygous - larger signal = mutant
Term
Cystic fibrosis
Definition
AR
prevalence of 1/25 (carriers) in caucasian
mutation of CFTR gene - over 1500 mutations possible
Term
Hemizygote
Definition
A male with a single allele at an X-linked locus
Term
Compound heterozygote
Definition
Individual with 2 different mutations at a single locus
Term
X-linked disorders
Definition
1/3 chance new mutation
2/3 chance inherited from mother
Term
MLPA
Definition
Mulitplex ligation dependent probe amplification
Compare possible carrier's DNA with control normal DNA and look for deletions/duplications of dystrophin gene
Term
Nucleotide repeat expansions
Definition
Dynamic mutations expand as they are passed on from generation to generation
Can occur anywhere within a gene
Term
HTT gene
Definition
CAG repeats in 1st exon of this gene can lead to Hungtington's Disease
>40 repeats
Term
DMPK gene
Definition
> 50 CTG repeats in 3' UTR leads to myotonic dystrophy
Term
Anticipation
Definition
You can see earlier onset/more severe symptoms as the gene is passed through generations
Term
Methylation analysis
Definition
Used to test for PWS/AS
Southern using methylation sensitive restriction endonucleases or PCR after treatment with bisulfite
>96% of Cs are methylated on maternal allele (around 15q) and barely any is methylated on paternal allele - can use this to determine maternal vs paternal alleles
-HPAII recognizes specific sequence only if not methylated = maternal doesn't cut, paternal does cut
-Bisulfite converts unmethylated Cs to Us (paternal) - then perform PCR with different primers
Term
Recurrence risks for PWS/AS
Definition
For deletions and UPD --> very small, 1/1000
For methylation defects, chromosome rearrangements, and UBE3A mutations --> up to 50%
Term
Driver mutation
Definition
Implicated in oncogenes
Confers advantage of cell growth
Term
Passenger mutation
Definition
Does not confer growth advantage but is present in cancerous cell genome
Term
Translocation in cancer
Definition
Leads to new product forming
OR
upregulation/downregulation of certain genes (oncogenes/tumor suppressor genes)
Term
Genetic heterogeneity
Definition
Mutations in different genes cause the same disease
ex. BRCA1 and BRCA2 both cause breast and ovarian cancers
Term
Cancer susceptibility genes
Definition
Usually autosomal dominant with incomplete penetrance
May appear to skip generations
Term
Two hit hypothesis
Definition
First hit may occur in germline or may be inherited (cancer susceptibility gene) and then second hit comes as a somatic mutation later in life

Tumor suppressor genes
Term
Familial cancer syndrome
Definition
Bilateral
Early onset
Term
Oncogenes
Definition
1 mutation can lead to cancer
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