Biochemistry Flashcards
What are the characteristics of Williams syndrome?
Congenital microdeletion of chromosome 7, patients have elfin facies, intellectual disability, heart problems, hypercalcemia, extreme friendliness with strangers
What is found in the first trimester ultra sound and serum level in Down syndrome? Second trimester quad screen?
US shows nuchal translucency and hypoplastic bone, low serum PAPP-A , HIGH free B hCG.
Second trimester quad screen shows low a FP, high free B hCG, low estriol, high inhibin A
What is found in the first trimester ultra sound and serum level in Edwards syndrome? Second trimester quad screen?
= Trisomy 18. low PAPP-A anddd low B hCG
Second shows low a FP, low B hCG, low estriol, low inhibin A
What is found in the first trimester ultra sound and serum level in Patau syndrome? Second trimester quad screen?
=Trisomy 13, low free b hCG andd low PAPP-A
What is VHL disease?
AD disorder, deletion of VHL gene on chromosome 3. Characterized by hemangioblastomas in retina, brain stem, cerebellum, spine, angiomatosis, , bilateral renal cell carcionomas, pheocytochromocytomas
What is shown on muscle biopsy of mitochondrial myopathies?
Ex: MELAS (mitochondrial encephalopathy, lactic acidosis, stroke like episodes) . Muscle biopsy shows ragged red fibers
What happens in a zinc deficiency?
Delayed wound healing, hypogonadism, alopecia, anosmia, acrodermatitis enteropathica
What is the most common urea cycle disorder and what are the symptoms?
Ornithine transcarbamylase deficiency (XR). elevated orotic acid in blood and urine, low BUN, symptoms of hyperammonia
What are the symptoms of I cell disease? where is the defective enzyme present?
Enzyme defect in N acetylglucosaminyl 1 phosphotransferase in the Golgi. Golgi can’t phosphorylate mannose residues destined for lysosomes. Results in growth failure, coarse facial features, clouded corneas, restricted joint movement, elevated serum lysosomal enzymes
What is the genetic mutation in Fragile X syndrome?
XD. Trinucleotide expansion (CGG) in FMR1 gene–> methylation and decreased expression. The second most common cause of genetic intellectual disability after Down syndrome
What is the difference between DNA polymerase III and I?
DNA polyermase III has 3 to 5 EXOnuclease activity which helps fix errors in mismatch .
DNA polymeriase I ALSO has 5 to 3 EXOnuclease activity to remove the RNA primer
What is the process from Gprotein activation of PLC to smooth muscle contraction?
Alpha subunit activates PLC which cleaves PIP2 into DAG and IP3. DAG directly activates PKC and IP3 releases calcium from ER which then activates PKC, which phosphorylates proteins and causes smooth muscle contraction
Describe RNA processing in eukaryotes. What are P bodies used for?
Occurs in nucleus. Initiall transcript is called hnRNA. Cap of 5’ with 7 methyl guanosine cap, poly A tail , splice out introns. = mRNA. Then transported out of nucleus where it is translated
mRNA quality control occurs at cytoplasmic processing bodies (P bodies) which contain exonucleases, decapping enzymes, and micro RNAs. mRNAs may be stored in P bodies for future translation
Describe the 3 steps of the splicing process of pre mRNA
- primary transcript combines with snRNPs and other proteins to form spliceosome
- lariat shaped intermediate is generated
- lariat is released to precisely remove intron and join 2 exons
Antibodies to spliceosomal snRNPs (anti smith antibodies) highly specific for SLE
Anti U1 RNP antibodies highly associated with mixed connective tissue disorder
What is the concept of wobble and unambiguity?
Unambiguous: each codon codes for amino acid
Degenerate: amino acids can have the same codon
Wobble: first two bases are required for base pairing, 3rd one results in the degenercy
