Exam 5 Flashcards
(91 cards)
1
Q
Helicase
A
Unwinds the 2 strands of parental DNA
2
Q
DNA Gyrase (Type II Topoisomerase)
A
Cuts DNA and allows it to relax. Relieves supercoiling.
3
Q
Single Strand Binding Protein (SSB)
A
Binds to newly separated individual DNA strands
4
Q
1st DNA polymerase III
A
Extends a primer continuously to build the leading strand
5
Q
Primase
A
Synthesizes short RNA sequences called primers
6
Q
Primers
A
Serve as a starting point for DNA synthesis
7
Q
2nd DNA polymerase III
A
Extends each RNA primer to complete an Okazaki fragment
8
Q
What strand is the Okazaki fragment on?
A
Lagging strand
9
Q
RNase H
A
Removes the RNA primer
10
Q
DNA polymerase I
A
Extends the newer Okazaki fragment with DNA
11
Q
DNA Ligase
A
Seals remaining nick between Okazaki fragments
12
Q
What does sealing the nick between Okazaki fragments do?
A
Creates a continuous lagging strand
13
Q
RNA Polymerase
A
Synthesizes RNA from DNA template
14
Q
DNA polymerase does not initiate polynucleotide synthesis, it…
A
Can only extend a preexisting chain
15
Q
What strand is synthesized in pieces?
A
Lagging strand
16
Q
What is transcription?
A
the process of copying a segment of DNA into RNA
17
Q
mRNA is also called what?
A
The transcript
18
Q
The site of protein synthesis
A
Cytosolic Ribosomes
19
Q
What strand is transcribed?
A
Template strand
20
Q
Noncoding strand/antisense
A
Template strand
21
Q
Coding strand/sense
A
Non-template strand
22
Q
How prokaryotic genes transcribe in tandem
A
Operons
23
Q
What side are promoters on?
A
5’
24
Q
Initiation: RNA polymerase binds to…
A
the promoter
25
Promoter
Tells RNA polymerase where to start, which direction to go in, and which strand of DNA to transcribe
26
Region of Pribnow Box
-10
27
-10 sequence
TATAAT
28
-35 sequence
TTGACA
29
Prokaryotic Elongation: RNA Polymerase
Unwinds DNA about 10 base pairs at a time
30
RNA transcript is ________ to the DNA template strand
antiparallel
31
Constitutive genes
Genes synthesized at a steady rate and required for basic cell function (housekeeping)
32
Inducible genes
Genes synthesized only when required by the cell
33
DNA base sequence for termination
AAGCGCCG (TTCGCGGC)
34
RNA hairpin for termination
Shortens the length of DNA-RNA hybrid helix, which is rich in easily separated A:U base pairs
35
Movement of Rho along RNA transcript in termination
Pushes polymerase forward, leaving a short hybrid helix from which the RNA more easily dissociates
36
Eukaryotic Transcription: RNA polymerase I
Synthesized precursors of most rRNAs and found in nucleoli
37
Eukaryotic Transcription: RNA polymerase II
Synthesizes mRNA in nucleus
38
Eukaryotic Transcription: RNA polymerase III
Synthesizes tRNA
39
What direction is RNA synthesized in?
5' to 3'
40
Eukaryotic Transcription: Initiation promoter
TATA box
41
What binds to the TATA box to allow more TFs to bind?
TF IID
42
What do transcription factors do?
Unwind DNA to form transcription bubble
43
What must assemble before RNA polymerase can bind to the promoter?
Transcription factors
44
Eukaryotic Transcription Elongation: Clamp
Accounts for processivity
45
Eukaryotic Transcription Elongation: Wall
Directs template strand out of the active site cleft
46
Eukaryotic Transcription Elongation: Pore
NTPs enter
47
Eukaryotic Transcription Elongation: Rudder
Separates RNA and template DNA strands
48
Eukaryotic Transcription Elongation: Bridge
Aids in translocation
49
What is processivity?
The ability of DNA polymerase to carry out continuous DNA synthesis on a template DNA without frequent dissociation
50
Transcription occurs in...
Nucleus
51
Translation occurs in...
Cytosol
52
How does addition of 5' cap occur?
7-methylguanine reside is joined to the 5'-nucleotide via 5'-5' triphosphate bridge
53
What are capped mRNAs resistant to?
5'-exonuclease cleavage
54
Approximately how long is a polyA tail?
80-250 nucleotides
55
What is the purpose of a polyA tail?
To protect against mRNA degredation
56
PolyA tail sequence
AAUAAA
57
What is AAUAAA signaling for?
For a protein to cleave, transcript, and extend with adenosine residues
58
Intron
Segment of a DNA or RNA molecule that does NOT code for proteins and interrupts the sequence of genes
59
Exon
Segment of DNA or RNA molecule containing information coding for a protein or peptide sequence
60
Purpose of splicing exons and excising introns
Required to produce mature mRNA that is competent to direct translation
61
Do introns or exons comprise a greater proportion of the gene?
Introns
62
What is translation?
The process of translating a sequence of nucleotides into a sequence of amino acids
63
tRNAs job is to match
an mRNA with the amino acid it codes for
64
Is tRNA the codon or anticodon?
Anticodon
65
What two structures are on the ends of a tRNA?
Anticodon on one end and aminoacyl group on the other end
66
How do amino acids attach to tRNA?
Via ester linkage at 3' OH
67
What enzyme attaches the correct amino acid to tRNA
Aminoacyl-tRNA synthetase
68
Where does the aa-tRNA pair with mRNA codon?
Ribosome
69
What is the molecular machine that performs biological protein synthesis?
Ribosome
70
How many tRNAs and mRNAs can bind to a ribosome at once?
3 tRNAs and 1 mRNA
71
Prokaryote subunit (70S)
30S and 50S
72
Eukaryote subunit (80s)
40S and 60S
73
E (exit) Site
Site occupied by tRNA from the previous donor tRNA-amino acid
74
P (peptide) site
tRNA-growing peptide chain
75
A (acceptor) site
Aminoacylation site
76
IF-3 binds where and does what?
Binds to 30S subunit and 50S dissociates
77
What complex binds to 30S subunit?
fMet-tRNAfMet with IF-2-GTP
78
What is the Shine-Dalgarno sequence?
AGGAGG
79
What does Shine-Dalgarno do?
Permits ribosome to select the proper AUG initiation codon
80
Do prokaryotes or eukaryotes lack Shine-Dalgarno?
Eukaryotes, the require at least 11 IFs
81
What makes the 50S subunit join 30S initiation complex?
IF-1 and IF-3 are released
82
Association of 50S with 30S triggers what?
IF-2 to hydrolyze its GTP
83
When 50S and 30S join, what happens to A and P site?
fMet-tRNAfMet occupies P site, while A site is ready to accept another aminoacyl tRNA
84
Translation Elongation: Decoding
Codon directed binding of incoming aminoacyl tRNA at the A site, and uncharges tRNA leaves E site
85
What ensures that polymerization does not occur unless the correct aminoacyl-tRNA is positioned in the A site?
EF-Tu
86
Translation Elongation: Transpeptidation
Catalyze peptide bond formation (peptide transferase activity)
87
Transfer of growing peptide goes from what site to another site?
P site to A site
88
Translation Elongation: Translocation
Move to the next codon. Peptidyl-tRNA and corresponding codon shifts to P site
89
What does EF-G do?
Displace peptidyl-tRNA
90
Termination of Translation (stop) codons
UGA, UAG, UAA
91
Where does the stop codon have to be positioned at?
A site
