FA - Biochemistry - Molecular (2016) Flashcards Preview

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Flashcards in FA - Biochemistry - Molecular (2016) Deck (49):
1

DNA exists in the condensed, chromatin form in order to ...?

Fit into the nucleus.

2

Negatively charged DNA loops ... around positively charged histone OCTAMER to form ...?

TWICE
NUCLEOSOME.

3

In mitosis, DNA condenses to form ...?

CHROMOSOMES.

4

DNA + Histone synthesis occurs during which phase?

S phase.

5

Barr bodies (inactive X chromosomes) are ...?

HETEROCHROMATIN.

6

Euchromatin:

Less condensed, appears lighter on EM!

7

Drugs that disrupt PYRIMIDINE SYNTHESIS:

1. Leflunomide.
2. Mtx.
3. TMP.
4. Pyrimethamine.
5. 5-FU.

8

Drugs that disrupt PURINE SYNTHESIS:

1. 6-MP.
2. Mycophenolate.
3. Ribavirin.

9

Drugs that disrupt BOTH PURINE + PYRIMIDINE SYNTHESIS:

HYDROXYUREA.

10

Orange "sand" in diaper?

LESCH-NYHAN ==> Sodium urate crystals.

11

Genetic code is universal - Exception in humans:

MITOCHONDRIA.

12

DNA replication - In both eukaryotes + prokaryotes, DNA replication is ...?

1. Semiconservative.
2. Involves both continuous + discontinuous (Okazaki fragment) synthesis.

13

Origin of replication:

Particular consensus sequence of base pairs in genome where DNA replication begins.
==> Single in prokaryotes.
==> Multiple in eukaryotes.

14

Origin of replication - What sequences are found in promoters and origins of replications?

AT-rich sequences.

15

Replication fork:

Y-shaped region along DNA template where leading + lagging strands are synthesized.

16

Helicase:

Unwinds DNA template at replication fork.

17

Topoisomerase II is also called ...?

DNA gyrase.

18

Fluoroquinolones inhibit ...?

BOTH topo II and topo IV.

19

Etoposide/teniposide inhibit ...?

EUKARYOTIC TOPO II.

20

Primase:

Makes an RNA primer on which DNA pol III can initiate replication.

21

DNA ligase:

Catalyzes the formation of a phosphodiester bond within a strand of double-stranded DNA (ie joins Okazaki fragments).

22

Splice site - Mutation:

Mutation at a splice site ==> Retained intron in the mRNA ==> Protein with impaired or altered function.

23

Mutations in splice sites are rare causes ...?

1. Cancer.
2. Dementia.
3. Epilepsy.
4. Some types of beta-thal.

24

Lac operon - Classic example of ...?

A GENETIC RESPONSE TO AN ENVIRONMENTAL CHANGE.

25

Role of the lac operon:

Glucose is the preferred metabolic substrate in E.coli, but when glucose is absent and lactose is available ==> The lac operon is activated to switch to lactose metabolism.

26

Mechanism of shift:

1. LOW GLUCOSE ==> Incr. AC activity ==> Incr. generation of cAMP from ATP ==> Activation of CATABOLITE ACTIVATOR PROTEIN (CAP) ==> Incr. transcription.
2. HIGH LACTOSE ==> Unbinds REPRESSOR protein from repressor/operator site ==> Incr. transcription.

27

State:
LOW glucose
YES lactose

Lac genes STRONGLY EXPRESSED.

28

State:
HIGH glucose
NO lactose

Lac genes NOT EXPRESSED.

29

State:
LOW glucose
NO lactose

Lac genes NOT EXPRESSED.

30

State:
HIGH glucose
YES lactose

Very low (basal) expression.

31

Protein synthesis is in which direction?

N-terminus to C-terminus.

32

What is the target of the 3-OH ATTACK?

THE TRIPHOSPHATE BOND.

33

Drugs blocking DNA replication often have ...?

MODIFIED 3-OH ==> Preventing addition of the next nucleotide ("chain termination").

34

Functional organization of a eukaryotic gene - From 5' to 3':

1. CAAT box (promoter).
2. TATA box (promoter).
3. Transcription start.
4. 5-UTR (in exon 1).
5. ATG (start codon - in exon 1).
6. Intron 1 (GT ... AG).
7. Exon 2.
8. Intron 2 (GT ... AG).
9. 3-UTR (in exon 3).
10. Polyadenylation signal (AATAAA - In exon 3 and IN 3-UTR).

35

RNA polymerases - Prokaryotes:

ONE RNA pol (multisubunit complex) ==> Makes all 3 kinds of RNA.

36

What inhibits RNA polymerase in prokaryotes?

RIFAMPIN.

37

What inhibits RNA polymerase in BOTH prokaryotes + eukaryotes?

ACTINOMYCIN D.

38

MicroRNAs:

Small, NONcoding RNA molecules that POST-TRASCRIPTIONALLY regulate protein expression.

39

Can introns contain miRNAs genes?

YES.

40

Can miRNA have MULTIPLE mRNA targets?

YES ==> Typically, related to complementary base pairing.

41

miRNA effect upon mRNA?

DEGRADATION or INACTIVATION of TARGET mRNA ==> Decr. TRANSLATION into PROTEIN.

42

Abnormal expression of miRNAs contributes to ...?

CERTAIN MALIGNANCIES ==> By SILENCING an mRNA from a tumor suppressor gene.

43

tRNA - Charging - Aminoacyl-tRNA synthetase:

ONE AMINOACYL-tRNA SYNTHETASE per AA.
==> "MATCHMAKER"/ uses ATP.

44

Aminoacyl-tRNA synthetase scrutinizes ...?

AA before + AFTER it binds to tRNA.
==> If incorrect bond is hydrolyzed.

45

The amino acid-tRNA bond has energy for ...?

FORMATION OF PEPTIDE BOND.

46

A mischarged tRNA reads ...?

USUAL CODON BUT INSERTS WRONG AMINO ACID.

47

What is responsible for the ACCURACY OF AA SELECTION?

1. Aminoacyl-tRNA synthetase.
2. Binding of charged tRNA to the codon.

48

tRNA CHARGING requires ...?

ATP.
==> tRNA Activation.

49

tRNA TRANSLOCATION requires ...?

GTP.
==> tRNA Gripping and Going places.