Flashcards in FA - Biochemistry - Molecular (2016) Deck (49):
DNA exists in the condensed, chromatin form in order to ...?
Fit into the nucleus.
Negatively charged DNA loops ... around positively charged histone OCTAMER to form ...?
In mitosis, DNA condenses to form ...?
DNA + Histone synthesis occurs during which phase?
Barr bodies (inactive X chromosomes) are ...?
Less condensed, appears lighter on EM!
Drugs that disrupt PYRIMIDINE SYNTHESIS:
Drugs that disrupt PURINE SYNTHESIS:
Drugs that disrupt BOTH PURINE + PYRIMIDINE SYNTHESIS:
Orange "sand" in diaper?
LESCH-NYHAN ==> Sodium urate crystals.
Genetic code is universal - Exception in humans:
DNA replication - In both eukaryotes + prokaryotes, DNA replication is ...?
2. Involves both continuous + discontinuous (Okazaki fragment) synthesis.
Origin of replication:
Particular consensus sequence of base pairs in genome where DNA replication begins.
==> Single in prokaryotes.
==> Multiple in eukaryotes.
Origin of replication - What sequences are found in promoters and origins of replications?
Y-shaped region along DNA template where leading + lagging strands are synthesized.
Unwinds DNA template at replication fork.
Topoisomerase II is also called ...?
Fluoroquinolones inhibit ...?
BOTH topo II and topo IV.
Etoposide/teniposide inhibit ...?
EUKARYOTIC TOPO II.
Makes an RNA primer on which DNA pol III can initiate replication.
Catalyzes the formation of a phosphodiester bond within a strand of double-stranded DNA (ie joins Okazaki fragments).
Splice site - Mutation:
Mutation at a splice site ==> Retained intron in the mRNA ==> Protein with impaired or altered function.
Mutations in splice sites are rare causes ...?
4. Some types of beta-thal.
Lac operon - Classic example of ...?
A GENETIC RESPONSE TO AN ENVIRONMENTAL CHANGE.
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.
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.
Lac genes STRONGLY EXPRESSED.
Lac genes NOT EXPRESSED.
Lac genes NOT EXPRESSED.
Very low (basal) expression.
Protein synthesis is in which direction?
N-terminus to C-terminus.
What is the target of the 3-OH ATTACK?
THE TRIPHOSPHATE BOND.
Drugs blocking DNA replication often have ...?
MODIFIED 3-OH ==> Preventing addition of the next nucleotide ("chain termination").
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).
RNA polymerases - Prokaryotes:
ONE RNA pol (multisubunit complex) ==> Makes all 3 kinds of RNA.
What inhibits RNA polymerase in prokaryotes?
What inhibits RNA polymerase in BOTH prokaryotes + eukaryotes?
Small, NONcoding RNA molecules that POST-TRASCRIPTIONALLY regulate protein expression.
Can introns contain miRNAs genes?
Can miRNA have MULTIPLE mRNA targets?
YES ==> Typically, related to complementary base pairing.
miRNA effect upon mRNA?
DEGRADATION or INACTIVATION of TARGET mRNA ==> Decr. TRANSLATION into PROTEIN.
Abnormal expression of miRNAs contributes to ...?
CERTAIN MALIGNANCIES ==> By SILENCING an mRNA from a tumor suppressor gene.
tRNA - Charging - Aminoacyl-tRNA synthetase:
ONE AMINOACYL-tRNA SYNTHETASE per AA.
==> "MATCHMAKER"/ uses ATP.
Aminoacyl-tRNA synthetase scrutinizes ...?
AA before + AFTER it binds to tRNA.
==> If incorrect bond is hydrolyzed.
The amino acid-tRNA bond has energy for ...?
FORMATION OF PEPTIDE BOND.
A mischarged tRNA reads ...?
USUAL CODON BUT INSERTS WRONG AMINO ACID.
What is responsible for the ACCURACY OF AA SELECTION?
1. Aminoacyl-tRNA synthetase.
2. Binding of charged tRNA to the codon.
tRNA CHARGING requires ...?
==> tRNA Activation.