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Biochem
FA Biochem Chapter
Question | Answer |
---|---|
Heterochromatin | Condensed, transcriptionally inactive |
Euchromatin | less condensed, transcriptionally active |
Amino acids necessary for purine synthesis | glycine, aspartate, glutamine |
Carbamoyl Phosphate | Involved in de novo pyrimidine synthesis and the urea cycle. OTC deficiency leads to a build up of carbamoyl phosphate, which gets shunted to orotic acid. Leads to high orotic acid levels |
Thymidylate Synthase | inhibited by 5 FU. converts dUMP to dTMP. Requires THF as a cofactor. |
Orotic Aciduria | Cannot convert orotic acid to UMP. AR. Increased orotic acid in urine, megaloblastic anemia not corrected by B12 or folate. Failure to thrive. No hyperammonemia (vs. OTC deficiency). Tx. Uridine |
ADA Deficiency | Converts adenosine to inosine. Excess ATP and dATP inbalances ribonucleotide pool and inhibits ribonucleotide reductase. Reduces DNA Synthesis, causes SCID. |
Lesch Nyan | Absence of HGPRT. HGPRT Converts hypoxanthine to IMP and guaninie to GMP. Excess uric acid production. Leads to mental retardation, agression, self mutilation, gout, choreoathetosis. |
Xeroderma Pigmentosum | UV light leads to formation of thymidine dimers. Normally resolved by nucleotide excision repair (endonuclease activity). Mutated in xeroderma pigmentosum - leads to melanoma and dry skin. |
Ataxia Telangectasia | increased sensitivity to ionising radiation leads to cerebellar ataxia, telangectasia, and immunodeficiency. |
Fanconi's Anemia | increased sensitivity to DNA cross linking agents leads to leukemia and aplastic anemia. |
tRNA | CAA sequence, and amino acid are at 3 prime end. Aminoacyl synthetase scrutinizes AA before and after it binds to tRNA. |
p53 and Rb | inhibit G1 to S progression. mutations results in unrestrained growth. |
SER | smooth endoplasmic reticulum. Site of steroid synthesis and detoxification of drugs and poisons. high in liver and adrenal cortex steroid producing cells. |
COP1 | retrograde trafficking from the Golgi to ER |
COP II | anterograde trafficking from the ER to cis golgi. |
Clathrin | trans golgi to lysosomes, to plasma membrane. to endosomes. RME |
I Cell Disease | inherited lysosomal storage disorder. Failure of M6P addition. Enzymes are secreted outside the cell instead of being targeted to lysosome. Coarse facial features, clouded corneas, restricted joint movement, high plasma levels of lysosomal enzymes. |
Type I Collagen | Bone skin tendon dentin fascia cornea late wound repair |
Type II Collagen | Cartilage, vitreous body, nucleus pulposis |
Type III Collagen | Reticulin: skin, blood vessels, uterus, fetal tissue, granulation tissue |
Type IV Collagen | basement membrane or basal lamina. especially for eyes, ears and kidneys |
Ehlers Danlos | Usually affects Type III Collagen. Hyperextensible skin, tendency to bleed, hypermobile joints. Can be autosomal dominant or recessive. Associated with joint dislocation, berry aneurysm, organ rupture. |
Osteogenesis Imperfecta | Brittle bone disease. Impaired matrix formation. Abnormal Type I Collagen causes multiple factures, blue sclera, hearing loss, and dental imperfection |
Alports Syndrome | XLR progressive hereditary nephritis, ocular disturbance, and deafness |
Elastin | Rich in proline and glycine, nonglycosylated. Tropoelastin has fibrillin scaffoling, which is deficient in Marfans. Broken down by elastase which is inhibited by alpha 1 antitrypsin. |
Prader Willi | Deletion of normally active paternal allele. (The maternal allele is normally imprinted). Mental retardation, hyperphagia, obesity, hypogonadism, hypotonia. |
Angelman's Syndrome | Deletion of normally active maternal allele. Mental retardation, seizures, ataxia, laughing. |
Achondroplasia | AD. Defect in FGFR-3. Dwarfism, short limbs, head and trunk are normal size. Associated with advanced paternal age. |
ADPKD | Bilateral. massive enlargement of cysts due to multiple large cysts. Flank pain, hematuria, hypertension, progressive renal failure. Increased risk for berry aneurysm, polycystic liver disease, mitral valve prolapse. Chromosome 16. |
Trinucelotide Repeat Disorders | Huntingtons (CAG); Myotonic Dystrophy (CTG); Fragile X (CGG); Friedreich's Ataxia (GAA) |
Trisomy21 | Downs. Mental Retardation, flat facies, epicanthal folds, simian crease, duodenal atresia, hirschsprungs, congenital heart disease, increased risk of ALL. Increased nuchal lucency on US. |
Quad Screen results for trisomy 21 | low AFP, increased beta HCG, reduced estriol, increased inhibin A. |
Edwards Syndrome | Trisomy 18. Severe mental retardation, rocker bottom feet, micrognathia, low set ears, clenched hands, prominent occiput. Death usually within one year |
Patau Syndrome | Trisomy 13. severe mental retardation, rocker bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, congenital heart disease. death usually within one year. |
increased AFP in quad screen | suggests neural tube defect, abdominal wall defects (omphalocele), multiple gestations, wrong birth date. |
Pericentric chromosomal inversion | a segment of a chromosome is reversed end to end, involves centromere and proceeds through meosis |
paracentric chromosomal inversion | a segment of a chromosome is reveresed and does not involve centromere. does not proceed through meiosis. |
Williams syndrome | congenital microdeletion of the long arm of chromosome 7. distinctive elfin facies, mental retardation, hypercalcemia due to increased vitamin D sensitivity, well developed verbal skills, extreme friendliness with strangers, CV problems. |
22q11 | CATCH 22. Digeorge - thymic, parathyroid, and cardiac defects. Velocardiofacial - palate, facial, and cardaic defects. Aberrant development of 3rd and 4th branchial pouches. |
Cri Cu Chat | congential microdeletion of short arm of chromosome 5. Microcephaly, moderate to severe mental retardation, high pitched crying, mewing, epicantal folds, CV abnormalities. |