First Aid USMLE Step 1 Biochemistry Laboratory techniques / genetics Flashcards

Terms Definitions
1) DNA is denatured by heating into 2 strands 2) cooling - premade DNA primers attach 3) heat stable DNA polymerase replicates
Southern, Northern, Western
SNoW DRoP - Southern = DNA, Northern = RNA, Western = Protein
antigen - antibody reactivity
Fluorescent probe binds to specific gene site of interest - picks up microdeletions
lacks introns - made by reverse transcriptase from tissue mRNA
Sanger DNA sequencing
Dideoxynucleotides halt DNA polymerase
cre-lox recombination
Cre-Lox recombination involves the targeting of a specific sequence of DNA and splicing it with the help of an enzyme called Cre recombinase.
RNAi––dsRNA use
complimentary to mRNA - transfected in human cells and degrades mRNA, knocking down gene expression.
1 gene has > 1 effect on an individual’s phenotype.
Differences in phenotype depend on whether the mutation is of maternal or paternal origin (e.g., AngelMan’s syndrome [Maternal], Prader-Willi syndrome [Paternal]).
Angelman's syndrome
deletion of normally active maternal allel (angelMan) - MR, SZAs, ataxia, inappropriate laughter (happy puppet)
Prader-Willi syndrome
deletion of normally active paternal allele (Prader, Paternal) - MR, obesity, hypogonadism, hypotonia.
Loss of heterozygosity
If a patient inherits or develops a mutation in a tumor suppressor gene, the complementary allele must be deleted/mutated before cancer develops. This is not true of oncogenes.
Dominant negative mutation
heterozygote produces a nonfunctional altered protein that prevents normal gene from functioning
linkage disequilibrium
2 linked loci occur more frequently than by chance.
cells in body have different genetic makeup (i.e. lyonization)
locus heterogeneity
mutations at different loci can produce the same phenotype
nl and mutated mtDNA - variable expression of mitochondrial inherited diseases
uniparental disomy
2 copies of chromosome from 1 parent and none from other
Adult Polycystic kidney disease (inheritance, gene, mech, sxs)
AD, bilateral kidney enlargement 2/2 cysts. Pain, hematuria, HTN, progressive renal failure, mutation in APKD1 (Chromosome 16). Associated with polycystic liver disease, berry aneurysms, MVProlapse. Juvenile form is recessive.
Familial hypercholesterolemia (hyperlipidemia type IIA) (inheritance, gene, mech, sxs)
AD, defective or absent LDL receptor - high LDL, MI, tendon xanthoma, atherosclerosis.
Marfan's syndrome (inheritance, gene, mech, sxs)
AD. Fibrillin gene mutation - skeletal abnomralities, CV (aortic incompetence, dissecting aortic aneurysm, floppy mitral valve), ocular - subluxation of lenses.
Neurofibromatosis type 1 (von Recklinghausen's disease) (inheritance, gene, mech, sxs)
AD long arm of 17 (17 letters in von Recklinghausen) - café au lait spots, neural tumors, lisch nodules, scoliosis, optic glioma, pheo, tumors
Neurofibromatosis type 2 (inheritance, gene, mech, sxs)
AD bilateral acoustic neuroma, juvenile cataracts - NF2 gene on chrom 22 (type 2)
Tuberous sclerosis (inheritance, gene, mech, sxs)
AD incomplete penetrance, variable presentation. Facial lesions (adenoma sebaceum), hypopigmented ash leaf spots on skin, cortical and retinal hamartoma, SZAs, MR, renal cysts and renal angiomyolipomas, increased incidence of astrocytomas
von Hippel Lindau disease (inheritance, gene, mech, sxs)
AD deletion of VHL (tumor suppressor) gene on 3p (3 words). Hemangioblastoma of retina/cerebellum/medulla, Renal cell carcinoma
Huntington's disease (inheritance, gene, mech, sxs)
ADchromosome 4 (hunting 4 food), dec GABA, Ach, depression, dementia, choreiform movements, caudate atrophy.
familial adenomatous polyposis (inheritance, gene, mech, sxs)
AD chromosome 5 (5 letters in polyp) APC gene, adenomatous polyps after puberty
Hereditary spherocytosis (inheritance, gene, mech, sxs)
AD spheroid RBCs, hemolytic anemia, inc MCHC, splenectomy cures
Achondroplasia (inheritance, gene, mech, sxs)
AD FGF receptor 3 defect. Associated with advanced paternal age.
cystic fibrosis (inheritance, gene, mech, sxs)
AR CFTR gene chrom 7, Phe 508 deletion, secretes Cl- in lungs and reabsorbes Cl- from sweat
Duchenne's MD (inheritance, gene, mech, sxs)
frame shift mutation, dystrophin deletion (ds), muscle breakdown. Before age 5, proximal weakness
Becker's MD (inheritance, gene, mech, sxs)
AR, mutated dystrophin gene, older onset
Fragile X syndrome (inheritance, gene, mech, sxs)
FMR1 gene - chromosmal breakage, triplet repeat (anticipation) 2nd most common MR, macro-orchidism, long face with large jaw, everted ears, autism.
Trinucleotide repeat diseases
Huntingtons, myotonic dystrophy, Friedreich's ataxia, Fragile X (try (trinucleotide) hunting for my fried eggs (x))
Edward's chromosome
18 - election age
Patau's chromosome
13 - puberty
prenatal markers for trisomies
↓-fetoprotein, ↑-hCG,↑ nuchal translucency
Pericentric chromosomal inversion
involves centromere, proceeds through meiosis
Paracentric chromosomal inversion
doesn't involve centromere, doesn't proceed through meiosis
deletion of short arm of 5, microcephaly, MR, cry, epicanthal folds, cardiac problems.
22q11 syndrome
CATCH-22 - Cleft palate, Abnormal facies, Thymic aplasia, T cell deficiency, Cardiac defects, hypocalcemia 2/2 to parathyroid aplasia, microdeletion at chrom 22q11, variable peentration as digeorge (thymic, parathyroid, cardiac defect) or velocardiofacial syndrome (palate, facial, and cardiac defects.
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