First Aid Biochemistry USMLE
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| Full term neonate of uneventful delivery becomes mentally retarded and hyperactive and has musty odorWHat is the diagnosis | PKU
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| Stressed executive comes home from work consumes 7 or 8 martinis in rapid succession before dinner and becomes hypoglycemicWHat is the mechanism | NADH increase prevents gluconeogenesis by shunting pyruvate and oxaloacetate to lactate and malate
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| 2 year old girl has increase in abdominal girth, failure to thrive and skin and hair depigmentation - what is the diagnosis | Kwashiorkor
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| Alcoholic develops rash, diarrhea and altered mental statusWhat is the vitamin defficiency | B3 (pellagra)
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| 20 year old male presents with idiopathic hyperbillirubinemiaWHat is the most common cause | Gilberts syndrome
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| 51 year old man has black spots on his sclera and has noted that urine turns black when he is standing | Alkaptonuria
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| 25 year old complains of chest pains and has xanthoma of Achilles tendonWhat is his disease and where is the defect | Familial hypercholesterolemia, lDL receptor
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| Condensed by negatively charged DNA looped twice around positively charged H2a, H2b, H3 and H4 histones (nucleosome bead) | Chromatin
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| _ ties nucleosomes together in a string (30 nm fiber) | H1 histone
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| Condensed, transcriptionally inactive chromatin | Heterochromatin
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| Less condensed, transcriptionally active chromatin | Euchromatin
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| Name purines | A, GPURe As Gold
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| Name pyrimidines | C, T, UCUT Pye
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| Which nucleotides have two rings? | Purines
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| WHich nucleotides have one ring? | Pyrimidines
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| Which nucleotide has a ketone | guanine
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| Which nucleotide has methyl | thymine
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| Deamination of cytosine makes _ | Uracyl
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| Uracil is found in _ Thymine is found in _ | Uracil - RNAThymine - DNA
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| Which bond is stronger GC or AT | GC (3 H bonds), AT is weaker (2 H bonds)
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| If GC content is increased what happens to melting temperature | Increases
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| Nucleotides are linked by _ | 3-5 phosphodiesterase bond
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| Substituting purine for purine or pyrimidine for pyrimidine is called ? | TransItion (identical)
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| Substituting purine for pyrimidine or vice versa | TransVersion (conVersion between types)
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| 4 features of genetic code | Unambiguous (each codon for only one amino acid)Degenerate (more then one codon can code for same amino acid)COmmaless, nonoverlappingUniversal
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| Name type of mutation - same amino acid, often base change in 3d position of codon tRNA wobble) | Silent mutation
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| Name type of mutation - changed amino acid (conservative - new amino acid is similar in chemical structure) | Missence mutation
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| Name type of mutation - change resulting in early stop codon | Nonsense mutation
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| Name type of mutation - change resulting in misreading of all nucleotides downstream, usually resulting in a truncated protein | Frameshift mutation
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| In prokaryotic replication, is there single or multiple origins of replication | Single origin of replication - continuous DNA synthesis on leading strand and discontinuous (okazaki fragments) on lagging strand
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| What is the role of primase in prokaryotic replication | Primase makes RNA PRIMER on which DNA polymerase III can initiate replication
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| Elongates the chain by adding deoxynucleotides to the 3 end until it reaches primer of preceding fragment | DNA polymerase III
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| Name enzyme that degrades RNA primer | 5'-3' exonuclease activity of DNA polymerase I
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| Has 5'-3' synthesis and proofreads with 3'-5' exonuclease | DNA polymerase III
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| Create a nick in the helix to relieve supercoils | DNA topoisomerases
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| Name DNA repair defects | Xeroderma pigmentosum (skin sensitivity to UV light)Ataxia-telangiectasia (x rays)Blooms syndrome (radiation)Fanconis anemia (cross linking agents)
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| Defective excision repair such as uvr ABC endonuclease. Results in inability to repair thymidine dimers, which form in DNA when exposed to UV light. Associated with dry skin and with melanoma and other cancersInheritance pattern | Xeroderma pigmentosumAutosomal recessive
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| In which direction is Dna and RNA synthesized | 5'-->3'
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