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Flashcards in Biochemistry Deck (255)
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1

Function of SER?

Steroid and phospholipid biosynthesis (adrenals, gonads, liver); detoxification (liver); sarcoplasmic reticulum in muscles

2

dTMP de-novo production

Catalyzed by thymidylate synthetase; 5,10-methyleneTHF + dUMP -> dihydrofolate + dTMP (dihydrofolate reductase)

3

Thalassemia intermedia

Associated with mutation 3 bases upstream from AUG in Kozak; Hypochromic, microcytic anemia

4

4 Types of Blots - detect what and probe?

Northern - RNA detection; ssDNA or RNA probe
Western - protein; Ab probe
Southern - DNA; ssDNA or RNA probe
Southwestern - DNA-binding protein; dsDNA
SNoW, DRoP

5

Which histone is not in the nucleosome core?

H1, which binds to nucleosome and linker DNA

6

Nucleosome characteristics?

Neg-charged DNA looped TWICE around histone OCTOMER (H2A, H2B, H3, H4)

7

Heterochromatin vs. euchromatin?

HeteroChromatin = Highly condensed
Euchromatin = true; transcriptionally active

8

Three major epigenetic mechanisms

DNA methylation of CpG islands represses transcriptions; histone methylation mostly represses; histone acetylation relaxes DNA coiling and makes DNA more active

9

Difference between uracil and thymine?

Thymine has methyl group

10

AA's necessary for purine synthesis

GAG - Glycine, Aspartate, Glutamine

11

Nucleoside v. nucleotide

Side = sugar + base; Tide = Sugar + base + phosphate

12

de novo purine synthesis how?

Ribose 5-P -> PRPP (PRPP synthase)
---> pathway (PRPP glutamyl amidotransferase = committed)
IMP ---> AMP or GMP

13

What drugs affect purine synthesis and where?

6-MP at PRPP amidotransferase; Mycophenolate, ribavarin at IMP -> GMP (IMP dehydrogenase); drugs affecting folate

14

What enzyme makes deoxyribunucleotides?

Ribonucleotide reductase;

15

de novo pyrimidine synthesis?

Glutamine, CO2, ATP -> Carbamoyl phosphate
+ asparatet -> Orotic acid
+ PRPP -> UMP -> UDP -> dUDP -> dUMP -> dTMP

16

Orotic aciduria mutation?

UMP synthase (= orotate phosphoribosyl transferase + OMP decarboxylase) mutation; megaloblastic anemia, lethargy, weakness, growth retardation; treated with uridine --> salvage pathway to make UMP, which inhibits CPS-II to dec. orotic acid production

17

What are the two major targeted enzymes involved in the creation of dTMP?

Made from dUMP via thymidylate synthase, which requires N5N10-methylene THF, which requires Dihydrofolate reductase

18

What drugs target dTMP synthesis?

5-FU targets thymidylate synthase; MTX, TMP, pyrimethamine target dihydrofolate reductase

19

Hydroxyurea acts on what enzyme?

Ribonucleotide reductase (the enzyme that makes deoxyribonucleotides; in particular the UDP -> dUDP version)

20

Two major enzymes of purine salvage pathway?

HGPRT - Guanine -> GMP; Hypoxanthine -> IMP
APRT - Adenine -> AMP

21

Major cause of AR SCID?

Adenosine deaminase deficiency: leads to increased dATP -| ribonucleotide reductase -> prevention of DNA synthesis -> dec. lymphocyte count

22

Lesch Nyhan?

Absent HGPRT -> guanine and hypoxanthine all turn into xanthine -> EXCESS uric acid. HGPRT - Hyperuricemia, Gout, Pissed off, Retardation, dysTonia. Tx = allopurinol (2nd - febuxostat; both xanthine oxidase inhibitors)

23

Only AA's coded by ONE codon?

AUG - methionine; UGG - tryptophan

24

DNA polymerases involved in prokaryotic DNA replication?

DNA pol I = degrades RNA primer (5'->3' exonuclease) and makes DNA. DNA pol III = major 5'->3' synthesis activity; 3'->5' exonuclease proofreading

25

Transition vs. transversion mutation?

Transition = same type; Transversion = different type; What sounds weirder?

26

Four types of DNA repair?

Nucleotide excision, base excision, mismatch, nonhomologus end joining (dsDNA ; ataxia telangectasia)

27

Nucleotide excision repair?

Endonucleases release oligonucleotide-containing damaged bases; Bulky distorting lesions
Xeroderma pigmentosum - defect prevents repair of pyrimidine dimers (UV exposure - the NUCLEAR option)

28

Base excision repair?

Base-specific glycosylase recogs then creates AP site. 1 or more nucleotides removed by AP-endouclease (5') and Lyase (3'); Non-bulky lesions; spontaneous/toxic deamination injury (purine->(hypo)xanthine); Quit stealing OTHER BASES

29

Mismatch repair?

MSH2 and MLH1 genes (MutS, MutL); Defective in HNPCC

30

mRNA stop codons?

U Go Away; U Are Away; U Are Gone;
UGA, UAA, UAG