Biochemistry - Genetics Flashcards
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| 10161987813 | -Sons of heterozygous mothers have a 50% chance of being affected. -No male-to-male transmission. -*Skips generations*. | X-linked recessive | 0 | |
| 10161989280 | X-linked recessive - Examples | *O*blivious *F*emale *W*ill *O*ften *G*ive *H*er *B*oys *H*er x-*L*inked *D*isorders: -*O*rnithine transcarbamylase deficiency -*F*abry disease -*W*iskott-Aldrich syndrome -*O*cular albinism -*G*6PD deficiency -*H*unter syndrome -*B*ruton agammaglobulinemia -*H*emophilia A and B -*L*esch-Nyhan syndrome -*D*uchenne (and Becker) muscular dystrophy | 1 | |
| 10162023445 | Females with ......... are more likely to have an X-linked recessive disorder. | Turner syndrome (45,XO) | 2 | |
| 12785180802 | X-inactivation (lyonization) | -One copy of female X chromosome forms a transcriptionally inactive Barr body. -Female carriers variably affected depending on the pattern of inactivation of the X chromosome carrying the mutant vs normal gene. | 3 | |
| 10162037002 | -Transmitted only through the *mother.* -*All offspring* of affected females may show signs of disease. -Variable expression in a population or even within a family due to *heteroplasmy.* | Mitochondrial inheritance |  | 4 |
| 10162042082 | Mitochondrial myopathies - Muscle biopsy | *"ragged red fibers"* (due to accumulation of diseased mitochondria in the subsarcolemma of the muscle fiber) |  | 5 |
| 10162054309 | Mitochondrial inheritance - Examples | 1) Mitochondrial myopathies -*MELAS* syndrome (*m*itochondrial *e*ncephalomyopathy, *l*actic *a*cidosis, and *s*troke-like episode -*MERRF* syndrome (*m*yoclonic *e*pilepsy with *r*agged *r*ed *f*ibers) 2) Leber hereditary optic neuropathy: bilateral vision loss | 6 | |
| 10162080750 | Autosomal dominant diseases - Examples | -*Familial adenomatous polyposis* -*Huntington* disease -Multiple endocrine neoplasias (*MEN*) -*Achondroplasia* -Most neurocutaneous disorders > *Neurofibromatosis* type 1 and type 2 > Tuberous sclerosis > von Hippel-Lindau disease | 7 | |
| 10162120977 | Autosomal recessive diseases - Examples | -Often due to *enzyme deficiencies* > *phenylketonuria* > *galactokinase deficiency* > *classic galactosemia* > glycogen storage diseases -*Cystic fibrosis* -*Sickle cell* anemia -Thalassemias | 8 | |
| 10162561933 | Most common lethal genetic disease in Caucasian population | Cystic fibrosis | 9 | |
| 10162570651 | Cystic fibrosis - Genetics | -*Autosomal recessive* -Defect in *CFTR* gene on chromosome 7 (commonly a deletion of ΔF508) | 10 | |
| 10162581517 | CFTR gene encodes ........... | *ATP*-gated Cl− channel that -*secretes* Cl− in lungs and GI tract -*reabsorbs* Cl− in sweat glands |  | 11 |
| 10162566635 | Cystic fibrosis - Pathophysiology | 1) Most common mutation (deletion of ΔF508) 2) *Misfolded protein* --- protein retained in RER and *not transported* to cell membrane 3) Decreased Cl− (and H2O) secretion 4) Compensatory *increased Na+ reabsorption* via ENaC (causes *more negative transepithelial potential difference*) 5) Increased H2O reabsorption 6) *Abnormally thick mucus* secreted into lungs and GI tract |  | 12 |
| 10162712234 | Cystic fibrosis - Diagnosis | 1) *High Cl− concentration* in pilocarpine-induced *sweat test* is diagnostic 2) *More negative transepithelial potential difference* 3) Contraction alkalosis and hypokalemia (because of ECF H2O/Na+ losses via sweating and concomitant renal K+/H+ wasting) 4) High immunoreactive trypsinogen (newborn screening) | 13 | |
| 10162794761 | Cystic fibrosis - Complications | 1) *Recurrent pulmonary* infections (eg, S aureus [infancy and early childhood], *P aeruginosa* [adulthood]), chronic bronchitis and bronchiectasis --- reticulonodular pattern on CXR, opacification of sinuses. 2) Nasal polyps 3) *Clubbing* of nails 4) *Chronic pancreatitis*, *pancreatic insufficiency*, malabsorption with steatorrhea, *fat-soluble vitamin deficiencies (A, D, E, K)* 5) Biliary cirrhosis, liver disease. 6) Meconium ileus in newborns. 7) *Infertility* in men (*absence of vas deferens*, spermatogenesis may be unaffected) and subfertility in women (amenorrhea, abnormally thick cervical mucus). 8) *Hyponatremia* (due to excessive salt wasting from sweat) | 14 | |
| 10162837869 | In cystic fibrosis, thick, viscous secretions in the lumen of the pancreas --- ............ | *obstruction*, inflammation --- *chronic pancreatitis*, fibrosis | 15 | |
| 10162851103 | Cystic fibrosis treatment in patients with ΔF508 deletion | combination of -lumacaftor (corrects misfolded proteins and improves their transport to cell surface) -ivacaftor (opens Cl- channels --- improved chloride transport) | 16 | |
| 10162859536 | ......... slows disease progression in cystic fibrosis. | Ibuprofen | 17 | |
| 10162943052 | Duchenne muscular dystrophy - Pathophysiology | *X-linked* disorder *Frameshift* deletions or *nonsense* mutations --- truncated or absent *dystrophin* protein --- progressive myofiber damage | 18 | |
| 10162964641 | Duchenne muscular dystrophy - Presentation/Findings | Onset before 5 years of age. 1) Weakness begins in *pelvic girdle* muscles and progresses superiorly. 2) *Pseudohypertrophy* of calf muscles due to *fibrofatty replacement* of muscle 3) Waddling gait 4) *Gowers sign:* patient uses upper extremities to help stand up 5) Asymmetric weakening of the paraspinal muscles --- *Kyphoscoliosis* 6) High *CK* and aldolase | 19 | |
| 10162983443 | Dystrophin - Functions | -Helps anchor muscle fibers, primarily in skeletal and cardiac muscle. -It connects the *intracellular cytoskeleton (actin)* to the *transmembrane proteins* α- and β-dystroglycan, which are connected to the extracellular matrix (ECM). | 20 | |
| 10163009162 | Gowers sign seen in .......... | Classically seen in *Duchenne* muscular dystrophy, but also seen in other muscular dystrophies and inflammatory myopathies (eg, polymyositis) | 21 | |
| 10163005670 | Becker muscular dystrophy - Pathophysiology | *X-linked* disorder *Nonframeshift* deletions in *dystrophin* gene (partially functional instead of truncated). | 22 | |
| 10163030451 | Becker muscular dystrophy - Presentation/Findings | -*Less severe* than Duchenne. -Onset in adolescence or early adulthood. -*Gower sign:* patient uses upper extremities to help stand up | 23 | |
| 10163045142 | -Autosomal dominant. -*CTG* trinucleotide repeat expansion in the DMPK gene --- abnormal expression of myotonin protein kinase --- myotonia (eg, difficulty releasing hand from handshake), muscle wasting -*CTG:* *C*ataracts, *T*oupee (early *balding* in men), *G*onadal atrophy | *Myotonic dystrophy type 1* | 24 | |
| 10163083386 | -Sporadic disorder seen almost exclusively in *girls* (affected males die in utero or shortly after birth). -Most cases are caused by de novo mutation of MECP2 on X chromosome. -Symptoms usually appear between ages *1-4*. -Characterized by > *regression* (*Rett*urn) in motor, verbal, and cognitive abilities > ataxia; seizures > *deceleration of head growth* > *stereotyped hand-wringing* | *Rett* syndrome | 25 | |
| 10177162527 | Fragile X syndrome - Pathophysiology/Genetics | > X-linked dominant inheritance. > Trinucleotide repeat (*CGG*) in FMR1 (Fragile X mental retardation 1) gene on the long arm of the X chromosome --- *hypermethylation* --- decreased expression > When the cells of the affected individuals are cultered in a medium, the area of increased repeats does not stain and appears "broken". --- Chromosomal studies typically show a *small gap* near the tip of the *long arm of the X* chromosome. | 26 | |
| 10177162528 | Fragile X syndrome - Presentation | *CGG:* *C*hin (long face with a *large jaw*, *large everted ears*) *G*iant *G*onads (post-pubertal *macroorchidism*) | 27 | |
| 10177209893 | Trinucleotide repeat expansion diseases | 1) Huntington disease: *CAG* (*C*audate has low *A*Ch and *G*ABA) 2) Myotonic dystrophy: *CTG* (*C*ataracts, *T*oupee [early balding in men], *G*onadal atrophy) 3) Fragile X syndrome: *CGG* (*C*hin [protruding], *G*iant *G*onads) 4) Friedreich ataxia: *GAA* (Ataxic *GAA*it) | 28 | |
| 10177248663 | Autosomal trisomies | 1) *D*own syndrome (trisomy *21*): *D*rinking age (21) 2) *E*dwards syndrome (trisomy *18*): *E*lection age (18). 3) *P*atau syndrome (trisomy *13*): *P*uberty (13) | 29 | |
| 10177264401 | Down syndrome - Presentation | 1) Intellectual disability 2) *Flat facies* 3) Prominent *epicanthal folds* 4) *Upward-slanting palpebral fissures* 5) Brushfield spots 6) *Protruding tongue* 7) *Short neck* and *generous nuchal skin* 8) *Single palmar crease* 9) Gap between 1st 2 toes 10) Incurved 5th finger 11) *Duodenal atresia* 12) Hirschsprung disease 13) Congenital heart disease (eg, *atrioventricular septal defect*) 14) Associated with early-onset *Alzheimer* disease (chromosome 21 codes for *amyloid precursor protein*) 15) Increased risk of *ALL* and AML | 30 | |
| 10177264402 | Down syndrome - Pathophysiology | 1) *95%* of cases due to *meiotic nondisjunction* (increases with advanced maternal age; from 1:1500 in women < 20 to 1:25 in women > 45 years old). 2) 4% of cases due to unbalanced *Robertsonian translocation*, most typically between chromosomes *14* and *21*. 3) Only 1% of cases are due to postfertilization mitotic error. | 31 | |
| 10177307733 | The 5 A's of Down syndrome: | 1) *A*dvanced maternal age 2) *A*tresia (duodenal) 3) *A*trioventricular septal defect 4) *A*lzheimer disease (early onset) 5) *A*ML/*A*LL | 32 | |
| 10177264403 | Down syndrome - Diagnosis | 1) First-trimester ultrasound: *Increased nuchal translucency* and hypoplastic nasal bone 2) 2nd trimester serum markers: *HI* up -β *h*CG: *high* -*I*nhibin A: *high* -AFP: *low* -Estriol: *low* | 33 | |
| 10177266154 | Edwards syndrome - Presentation | *PRINCE* Edward: -*P*rominent occiput -*R*ocker-bottom feet -*I*ntellectual disability -*N*ondisjunction -*C*lenched fists (with overlapping fingers) -low-set *E*ars -*micrognathia* (small jaw) -*congenital heart disease* -omphalocele | 34 | |
| 10177346321 | Edwards syndrome- Diagnosis | 2nd trimester serum markers: -β hCG: *low* -AFP: *low* -Estriol: low | 35 | |
| 10177346322 | Patau syndrome - Presentation | 1) micro*P*hthalmia 2) microce*P*haly 3) holo*P*rosencephaly 4) cleft li*P*/*P*alate 5) *P*olydactyly 6) cutis a*P*lasia 7) *P*olycystic kidney disease 8) Om*P*halocele 9) congenital heart disease (*P*ump) 10) severe intellectual disability 11) rockerbottom feet | 36 | |
| 10177381896 | Patau syndrome - Diagnosis | 1st trimester serum markers: -β hCG: *low* -PAPP-A: *low* | 37 | |
| 10181675519 | -Chromosomal translocation that commonly involves chromosome pairs 13, 14, 15, 21, and 22. -One of the most common types of translocation. -Occurs when the long arms of 2 acrocentric chromosomes (chromosomes with centromeres near their ends) fuse at the centromere and the 2 short arms are lost. | Robertsonian translocation | 38 | |
| 10181680431 | Congenital deletion on short arm of chromosome 5 (46,XX or XY, 5p−). Findings: -microcephaly -moderate to severe intellectual disability -high-pitched crying/meowing -epicanthal folds -cardiac abnormalities (VSD). | Cri-du-chat syndrome | 39 | |
| 10181682602 | Congenital microdeletion of long arm of chromosome 7 (deleted region includes elastin gene). Findings: -distinctive "elfin" facies -well-developed verbal skills -extreme friendliness with strangers -intellectual disability -hypercalcemia -cardiovascular problems (eg, supravalvular aortic stenosis, renal artery stenosis) | Williams syndrome |  | 40 |
| 10181689000 | 22q11 *microdeletion* syndromes | 1) *DiGeorge* syndrome: thymic, parathyroid, and cardiac defects. 2) *Velocardiofacial* syndrome: *palate*, cardiac and facial defects. | 41 | |
| 10181692497 | 22q11 *microdeletion* syndromes due to ........... | aberrant development of *3rd* and *4th* branchial (pharyngeal) *pouches* | 42 | |
| 10181696759 | DiGeorge syndrome - Presentation/Findings | 1) Thymic aplasia --- *T-cell deficiency* 2) Failure of parathyroid development --- hypocalcemia. 3) Cardiac defects (*Truncus arteriosus*, *tetralogy of Fallot*) | 43 |