Replication, Transcription, Protein Synthesis

Question 1

DNA polymerase

Answer 1

replication

Question 2

RNA polymerase

Answer 2

transcription

Question 3

Ribosomes

Answer 3

translation

Question 4

Replication

Answer 4

semi conservative
half old and half new
continuous and Okazaki fragments
template directed synthesis 5’–>3’

Question 5

Replication Mismatch Repair

Answer 5

older strand is methylated
unmarked strand with error is corrected
segment around mutation is excised and replaced by DNA polymerase

Question 6

Transcription

Answer 6

template-directed synthesis 5’–>3’

Not continuous like Replication

Question 7

Transcription Initiation Complex

Answer 7

multi-protein complex built upstream of Promoter
Transcription factos recognize specific DNA sequences proximal and distal
DNA bends/loops for protein - protein interaction
complex recruits RNA Polymerase II

Question 8

Enhancers/Regulatory sequences

Answer 8

bind proteins to attract or block RNA polymerase

Question 9

Promoters

Answer 9

binding site for RNA polymerase

start site for transcription

Question 10

Terminator

Answer 10

sequence site that causes RNA polymerase to fall off

Question 11

Eukaryotic Transcription complex

Answer 11

Core Promoter contains TATA sequence that binds TFs
Proximal elements - bind specific factors
Distal elements - bind TFs, enhancers- activators, hormone response elements
Co-Activation Complex- does not bind to DNA, protein-protein interaction
RNA polymerase II- recruited + disengage cts
complex stays bound during multiple rounds of initiation

Question 12

Bacteria - transcription and translation

Answer 12

coupling/linked
both occurs in cytoplasm
protein synthesis begins before gene transcription is completed
very fast gene expression response

Question 13

Genes can be switched on to adapt to new nutrients

Glucose –> Lactose

Answer 13

once glucose is depleted
genes for lactose digestion is turned on to use lactose for energy
Diauxic growth
beta-galactodase cleaves lactose –> glucose + galactose

Question 14

Eukaryotes- Transcription and Translation

Answer 14

Transcription in Nucleus
mature mRNA transported thru nuclear pores
Translation in cytoplasm
mature mRNA binds Translation factors and Ribosomes

Question 15

Eukaryotes initial RNA transcript is processed

Answer 15

5’ end capped m7GpppG
3’ end cleaved and polyadenylated
introns spliced

Question 16

Eukaryotic Translation components

Answer 16

"protein synthesis"
energetically costly- GTP /ATP 
mRNA - codon
tRNA- charged with AA, anticodon 
ribosome- catalyzes peptide bond formation
Translation factors -  eIFs

Question 17

Eukaryotic Translation Initiation

Answer 17

eIF-GTP recruits
40S binds to mRNA
60S binds now forming 80S ribosome
Met-tRNA binds to P site (AUG)

Question 18

Eukaryotic Translation Elongation

Answer 18

eEF1-GTP-tRNA 
A site for second charged tRNA   
peptidyl transfer catalyzed by 28S rRNA unit 
80S ribosome  moves 3nt (1 codon)
1 GTP- hydrolysis for delivery 
1 GTP- translocation 
uncharged tRNA moves over to E site  and P site
opening A site

Question 19

Eukaryotic Translation Termination

Answer 19

Release Factors (RFs) recognize stop codon in A site
eRF1 stimulates ribosome to catalyze peptidyl transfer but no AA is present for stop codons
Water - nucleophilic attack => hydrolyzes peptide chain from tRNA and release protein
other RFs causes dissociation translation complex

Question 20

Tetracycline

Answer 20

antibiotic
binds to A site of 30S
reversibile

Question 21

Erythromycin

Answer 21

antibiotic

blocks peptidyl transferase activity in 50S subunit

Question 22

Chloramphenicol

Answer 22

antibiotic
blocks aminoacyl-tRNA binding to 50S
can also inhibit Euk mito translation

Question 23

Streptomycin, Neoycin, Gentamycin

Answer 23

antibiotic
bind to 30S subunit
causes codon misreading
nonfunctional proteins

Question 24

Diptheria toxin

Answer 24

euk translation toxin
ADP ribosylates eEF2 to block 80S translocation
prevents translocation of peptide chain from A site to P site
uses NAD+

Question 25

Ricin

Answer 25

N-glycosidase enzyme that blocks eEF1 and eEF2
removes single adenine base from ribose
inactives 60S subunit by cleaving 28S rRNA