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Step 1 3.1.13 (2)


What is codominance what what is an example? neitehr of 2 alleles is dominant= Blood groups A, B,AB
What is variable expression and what is an example? pheontype and severity vary from personm to person. ex. 2 people with neurofibromatosis type I can can different presentations
What is incomplete penetrance? not all people with mutant genotype show the mutant phenotype
What is pleiotropy? What is an example 1 gene>1 effect on a persons phenotype. Ex. PKU has many sx from retardation to hair and skin changes
What is imprinting and what is example? differences in phenotype depend whether the mutation is maternal or paternal in origin. ex. Prader-Willi and Angelman's syndrome
What is anticipation and what is an example? severity of disease is worse or age of onset is earlier in succeeding generations. Ex. huntington's
What is loss of heterozygosity? What is an example? patient inherits a mutation in a tumor surpressor gene. the complimentary allele also has to be deleted or mutated before disease develops. (not true for oncogenes). Ex. retinoblastoma
What is a dominant negative mutation. What is an example? heterozygote produces a nonfunctional altered protein that prevents the normal from working. Ex. TF is mutated in allosteric site. nonfunctiong mutant binds DNA preventing wild type bidning
What is linkage disequilibrium? tendency for certain alleles at 2 linked loci to occur together more often than by change. measured in populations
What is mosaicism? cells in body differ in genetic makeup due to postfertilization loss of genetic material, can be germline and produce disease not found in parental cells
What are the 2 Hardy Weinberg equations? p2 + 2pq+ q2=1, p+q=1
What might cause a hematologic mosaic individual? mutation in the embryonic precursor of bone marrow stem cell
What is the origin of a chimeric individual? 2 zygotes that subsequently fuse
What is locus heterogeneity and what are some examples? mutation at different loci can produce same phenotype. Ex. Marfan's, MEN2B, and homocystinuria all cause marfanoid habitus.
What is heteroplasmy? presence of both normal and mutated mtDNA resulting in variable expression in mitochondrial inherited disease
What is uniparental disomy? offspring receives 2 copies of a chromosome from one parent and none from the other
How do you calculate the frequency of homozygosity for a given allele in Hardy-Weinberg equilibrium? p2 for p, q2 for q.
how do you calculate the frequency of heterozygosity for a given allele ( carrier frequency) in Hardy Weinberg equilibrium? 2pq
What is the freqiuency of an X linked recessive disease in males vs females in Hardy Weingberg equilibrium? males=q, females=q2
What are the 4 major assumptions in Hardy Weingberg equilibrium? 1. no mutation at locus 2. no selection for genotypes at locus 3. random mating 4. no migration
What is imprinting? at a given loci, only 1 allele is active other is inactivated. If you delete the active allele it results in disease
What chromosome is affected in both Prader Willi and Angelman syndromes? What other mech could they happen from? both invovled Chr 15. Can also result from uniparental disomy
Patient has mental retardation, hyperphagia, obesity, hypogonadism, and hypotonia. Dx and Mech? Prader-Willi Syndrome. individual has normally inactivated maternal allele, paternal allele should be active but is deleted
Patient has mental reatrdation, seizures, ataxia, and inappropriate laughter. Dx and mech? Angelman's syndrome. individual has a normally inactivated paternal allele. The maternal allel should be active but it's deleted
What types of things tend to be autoD? Who is affected in a pedigree? often due to defect in structural genes. many generations both male and female are affected
When do AutoD disease tend to present? often pleiomorphic and present after puberty
What types of things tend to be autoR? What is seen on pedigree? 25% of offspring from 2 carrier parents are affected. often seen in enzyme deficiencies. usually seen in only 1 generation
When do autoR present? commonly more severe than autoD, often present in childhood
What is seen in a pedigree in XLR? sones of heterozygous mothers have 50% chance of being affected. no male to male transmission
What are some common presentation of XLR? disease is more severe in males, females have to be homozygous to be affected
What is seen in pedigree in an XLD? transmitted thru both parents. either male or female of an affected mother can be affected. ALL female offspring of an affected father are affected
Patient has incr phosphate wasting at the proximal tubule. rickets like presentation. DX and inheritance? Hypophosphatemic rickets. XLD
What is seen in a pedigree of mitochondrial inheritance? transmitted only through mom. All offspring of affected females can show disease. often due to failures in oxidative phosphorylation
On microscopy, ragged red fibers are seen. DDX and inheritance? loss of central vision: Leber's hereditary optic neuropathy, myoclonic epilepsy, mitochondrial encephalopathy. Mitochondrial myopathies that are mitochondrial inheritence
Patient has dwarfism, short limbs but head and trunk are normal sized. Dx and mech and inheritance? What could be a causal factor? Dx: Achondroplasia. Mech: cell signaling defect og fibroblast growth factor receptor 3. Inh: AutoD. Associated with advanced paternal age
Adult Pt present with flank pain, hematuria, HTN, and progressive renal fialure. bilateral kidney enlargement. Dx and mech and inheritance? What are some key associations? Dx: AutoD polycystic kidney disese Mech: mutation in PKD1 (90%) Inh: Auto D. Assocaitons: polycystic liver, berry aneurysm, mitral valve prolapse
Pt present with adenomatous polyps in colon after puberty. Dx and mech and inheritance? Dx: familial adenomatous polyposis. Mech: mutation of APC gene on Chr 5. Inh: AutoD
Severe atherosclerotic disease early in life, achilles tendon xanthoma. possible MI before age 20. Dx and mech and inheritance? Dx: familial hypercholesterolemia (HLD type IIA). Mech: defective or absent LDL receptor. Inh: Auto D. heterozygotes usally have cholesterol around 300
Pt has telangiectasia, recurrent epistaxis, skin discoloration, and ateriovenous malformations. Dx and inheritance? Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu)
Pt has a hemolytic anemia and an incr mean corpuscular Hb concentration and FHx of same. Dx and mech and inheritance? Tx? Hereditary spherocytosis due to spectrin or ankyrin defect. Auto D. Tx: splenectomy
20-50 y/o pt comes in with depression, progressive dementia, chorea, caudate strophy and decr levels of GABA and Ach in the brain. Dx and mech and inheritance? Dx: Huntington's disease. MEch: CAG repeat on chr 4. Inh: AutoD
Pt is tall with long extremities, pectus excavatum, hyperextensive joint and arachnodactyly. Dx and mech and inheritance? Key associations? Dx: Marfan's syndrome Mech: fibrillin gene mutation affecting skeleton heart, eyes. Inh: autoD. Assoc: cystic medial necrosis of aorta ( dissection), floppy mitral valve and subluxation of lens
What gene mutation are MEN2A and 2B associated with? ret gene
Pt comes in with cafe-au-lait spots, neural tumors, pigmented iris hamartoms (lisch nodules) and possilbe scoliosis or optic gliomas. Dx and mech and inheritance? Dx: Neurofibromatosis type 1. Mech: mutation on long arm of Chr 17. Inh: AutoD.
Pt comes in with bilatreral acoustic schwannomas, juvenile cataracts. Dx and mech and inheritance? Dx: Neurofibromatosis type 2. MecH: NF2 gene on Chr 22. Inh: autoD
Pt comes in with facial lesions, ash leaf spots on skin, cortical and retinal hamartomas, seizures, retardation, renal cysts and renal angiomyolipoma, cardiac rhabdomyoma or astrocytoma. Dx and inheritance? Dx: tuberous sclerosis Inh: autoD
Patient comes in with hemangioblastomas of retina or cerebellum or medulla. possible bilateral renal carcinoma. Dx and mech and inheritance? Von Hippel-Lindau disease. Mech: deletion of VHL tumor surpressor on Chr 3. results in constuitive expression of HIF transcription factor. Inh: AutoD
Patient comes in with recurrent pulmonary infections with Pseudomonas and S. aureus, chronic bronchitis, bronchiectasis, pancreatic insufficiency, nasal polyps, meconium ileus. and possib;le infertility. Dx and mech and inheritance? Dx: cystic fibrosis Mech: autoR defect in CFTR on Chr 7 usually DF508 abnormal folding Inh: autoR
What is the diagnostic test for cystic fibrosis? sweat test for Cl- ions
What is the major Tx for CF? N-acetylcystein to loosen mucus lugs (cleaves disulfide bonds)
What is a mnemonic for the XLR disorders? Be Wise Fools GOLD Heeds Silly Hope: (Burton's agammaglovbulinemia, Wiskott-Aldrich, Fabry's, G6PD def, Ocular albinism, Lesch-Nyhan, Duchennes MD, Hunter's Syndrome, Hemophilia A and B
Why are female carriers rarely affect by XLR? due to random deactivation of X in each cell
A 4 yr old pt comes to the office and need its upper extremities to stnad up. cardiac myopathy is seen as well as calf hypertrophy. Dx and mech and inheritance? Dx: Duchenne's MD Mech: XL frame shift deletion of the dystrophin gene and accelerated muscle breakdown. Starts at pelvic girlde
What is the best diagnostic test for Duchenne's MD? incr in CPK and muscle biopsy
What is the difference b/w Becker's and Duchenne MD? Becker's is a mutation but no frameshift in the dystrophin gene. Onset is in adolescence or early adulthood as opposed to <5y/o in Duchenne MD
Pt presents with macroorchidism (big testes), long face with large jaw, large everted ears, autism and mitral valve prolapse. Dx and mech and inheritance? Dx: Fragile X syndrome Mech: CGG repeat and inappropriate methylation of FMR1 gene. Inh: XLR
What are 4 trinucleotide repeat disorders? Huntington's, myotonic dystrophy, Friedrich's ataxia, fragile X
What disease has a CGG repeat? Fragile X
What disease has a GAA repeat? Friedrich's ataxia
What disease has a CAG repeat? Huntington's
What disease has a CTG repeat? Myotonic dystrophy
A pt comes in with mental retardation, flat facies, epicanthal folds, simian crease, a gap b/w 1st 2 toes, duodenal atresia and ASD. Dx and mech and inheritance? Dx: Down Syndrome Mech: trisomy 21 meiotic nondisjunction associated with advanced maternal age Inh: autosomal
A U/s with incr nuchal translucency is assoc with? Down syndrome
A pregnancy screen test with decr alpha fetoprotein, incr beta HCG, decr estriol and incr inhibin A suggest? Down Syndrome
A pt has severe mental retardation, rocker bottom feet, micrognathia, low set ears, clenched hands, CHD. Dx and mech and inheritance? Dx: Edwardss syndrome Trisomy 18 Mech: nondisjunction
A pregnancy screen showin decr alpha fetoprotein, decr Beta HCG, decr estriol, and normal inhibin A is suggestive of? Edwards syndrome: Trisomy 18
A child with severe retardation, rocker bottom feet, cleft lip/palate, holoprosencephaly, polydactyly, CHD. Dx and mech and inheritance? Dx: Patau's syndrome: trisomy 13
A pregnancy screen with normal alphja fetoprotein, normal Beta hCG, normal estriol, and normal inhibin in the setting of retardation is? Pataus syndrome: trisome 13
What Chr are most likely to undergo a Robertsonian translocation? 13,14,15,21,22
Pt has microcephaly, moderate retardation, high pitched crying or mewing, epicanthal folds, and VSD. Dx and mech and inheritance? Dx: Cri-du-chat syndrome (cry of the cat) Mech: congenital microdeletion of short arm of Chr 5
Child with elfin facies, mental retardation, hypercalcemia (incr sensitivity to vit D), well developed verbal skills and extreme friendliness with strangers. Dx and mech and inheritance? Dx: Williams Syndrome Mech: congential microdeletion of long arm of chr 7 (incluses elastin gene)
Pt with cleft palate or abnormal facies, Thymic aplasia, cardiac defects, hypocalcia secondary to parathyroid aplasas most likely has what chromosomal abnormality? What development is poor? 22q11 deletion, abberant development of the 3rd and 4th branchial pouches
A pt with thymic, parathyroid and cardiac congenital defect has? DiGeorge syndrome: deletion of 22q11
A patient with palate, facial and cardiac defect has? Velocardiofacial syndrome: 22q11 deletion
Created by: tjs2123



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