1: Fundamentals of PCR (MIDTERMS) Flashcards
The process of making/amplifying DNA copies outside of the body/ in vitro
Polymerase Chain Reaction (PCR)
Vitro means?
Outside of the body
How many kilobase of DNA are amplified in most PCR methods
up to 10 kbs
PCR mirrors what mechanism in its procedure?
DNA replication
What are the 2 reasons why we perform PCR?
- DNA fingerprint (for suspect identification)
- Disease identification (analysis of diseases)
Enumerate the 3 main steps of PCR
- Denaturing
- Primer Annealing/Binding
- Elongation/extension
3 main step of PCR:
→ DNA is subjected at 95ºC for 30 to 60 seconds in order to separate/unwind
→ Mimics the function of helicase in cells
Denaturation of DNA
What temperature and how many seconds is the process of denaturation of DNA in PCR?
95ºC for 30 to 60 seconds
T or F
Denaturation of DNA is a step in PCR that can be skipped and is not important
F (CANT BE SKIPPED since it is important for DNA to be exposed and primers to bind)
3 main step of PCR:
→ The primers bind to their complementary sequences on the single DNA strands
Primer annealing/binding
T or F
In primer annealing/binding , primers bind to target sequence and are chosen based on similarand non complementary relationship with target sequence
F (primers are chosen based on their COMPLEMENTARY BINDING relationship with target sequence)
What primers exist in PCR?
Forward and Reverse primers
Temperatures for primer annealing depends on what?
G+C content (guanine and cytosine)
T or F
Higher g+c content, higher melting temperature
T
Indication of melting temperature of DNA?
If half of the strands are in single-stranded state
3 main step of PCR:
→ at 72ºC, DNA polymerase adds nucleotides to the 3’ ends of the primers and is extended
Elongation/extension
3 main step of PCR: Elongation
These are building blocks of DNA polymerase
dNTPS
What temperature in elongation/extension process of DNA in PCR?
72ºC
3 main step of PCR: Elongation
DNA polymerase adds nucleotides where?
3’ ends of the primers
3 main step of PCR: Elongation
In what direction does DNA polymerase run along?
5’→3’ direction
3 main step of PCR: Elongation
What strand direction favors the polymerase?
strand running on 3’→5’
T or F
Extension starts at primers and attaches at appropriate nucleotide
T
Final extension cycle runs for how long at what temperature
10 minutes at 72ºC followed by incubation at 4ºC
T or F
DNA polymerase typically functions at 80ºC
F (37ºC, anything lower or higher could cause it to not perform its function well)
This polymerase used in PCR is a heat stable bacteria purified from hot springs in 1976
Thermus aquaticus (Taq DNA polymerase)
T or F
Size of the DNA fragment produced is dependent on size of the polymerase
F (dependent on the size of the PRIMER; longer sequence, longer primers)
At each PCR cycle, the number of DNA molecules is increased to how many?
Doubled
If you subject your target DNA to 10 cycles, you end up with how many copies of DNA?
1, 024 copies of DNA
(2^n lng bb)
If you subject your target DNA to 7 cycles, you end up with how many copies of DNA?
128 copies of DNA
(2^n lng bb)
T or F
If you start with 2 unwound strands, first cycle produce 4 strands of DNA, While 3rd produces 8
T
(basta doubled lang bb)
Produced DNA depends on?
number of cycles set for thermal cycler
Temperature and time for primers annealing/binding?
40-65 ºC, 30-60 seconds
3 main step of PCR: Primers annealing/binding
T or F
temperature usually set for primers with higher g + c content are usually set 10 ºC-20 ºC below the melting temperature
T
3 main step of PCR: Primers annealing/binding
Higher g + c content = ?
Higher g + c content = higher melting temperature
3 main step of PCR: Primers annealing/binding
T or F
the annealing temperature of DNA is where half of the strands are in a single-stranded state
F (the MELTING temperature of DNA is where half of the strands are in a single-stranded state
thrives in hot temperatures hence it only needs to be added once at the beginning of the procedure
Thermus aquaticus Taq DNA polymerase)
maximal enzymatic activity of Taq Polymerase?
75-80ºC
DNA Polymerase functions at what temp?
37ºC
Enumerate the process of PCR
- Denaturation
- Primer Annealing
- Elongation
functions ideally at 37ºC
a. DNA Polymerase
b. Taq Polymerase
c. Both
e. NOTA
a. DNA Polymerase
95ºC for 30 to 60 seconds
a. Annealing
b. Elongation
c. Both
e. NOTA
e. NOTA (DENATURATION temp yan)
40-65ºC for 30-60 seconds
a. Annealing
b. Elongation
c. Both
e. NOTA
a. Annealing
72ºC for 10 mins
a. Annealing
b. Elongation
c. Both
e. NOTA
b. Elongation
mimics function of helicase
a. Elongation
b. Denaturation
c. Both
e. NOTA
b. Denaturation
requires melting temperature
a. Annealing
b. Elongation
c. Both
e. NOTA
a. Annealing
95ºC for 5 mins (acc sa table)
a. Initial Denaturation
b. Denaturation
c. Both
d. NOTA
a. Initial Denaturation
94ºC for 1 min (acc sa table)
a. Initial Denaturation
b. Denaturation
c. Both
d. NOTA
b. Denaturation
55ºC for 1 min
a. Annealing
b. Denaturation
c. Both
d. NOTA
a. Annealing
72ºC for 1 min
a. Extension/Extension
b. Final Elongation
c. Both
d. NOTA
c. Both
4ºC to infinity
a. Annealing
b. Denaturation
c. Both
d. NOTA
d. NOTA (hold temp yn bb)
What are the essential requirements for PCR?
- Template dNA
- Pair of Primers
- Thermostable DNA polymerase
- dNTPS
- Cations and Buffer
- Nuclease-free water
- Thermocycler
Range of length of primers?
15 to 30 nucleotides
Essential requirements for PCR:
→ are synthetic oligonucleotides that serve to initiate DNA synthesis
→ short pieces of single-stranded DNA that are complementary to the 2 ends of each target DNA
→ each one provides the 3ʼOH group required to form a covalent bond (phosphodiester) with another nucleotide
Primers
4 dNTPs used?
dTTP, dCTP, dGTP, and dATP
recommended concntration of each dNTP?
200-250μM
T or F
Less than 4mM concentration of dNTP is inhibitory
F (MORE THAN 4mM concentration of dNTP is inhibitorykasi magcchelate mg2)
are usually supplied with PCR enzymes at an amount that gives a working concentration of 1.5mM when diluted
Mg^2+
may contaminate and degrade DNA including the primers, template, and amplified product
Nuclease
T or F
Nuclease-free water must be stored in small aliquots to reduce contamination
T
a machine that automatically changes the temperatures and incubation times in each cycle
Thermocycler
Optimal length of primer?
18-25 nucleotides
15-30 nucleotides
a. Range of primers
b. Optimal length of primers
c. NOTA
a. Range of primers
18-25 nucleotides
a. Range of primers
b. Optimal length of primers
c. NOTA
b. Optimal length of primers
long repeats of any base are avoided to minimize?
secondary structures
T or F
minimize secondary structures by avoiding long repeats of any base as these cause a increase in available primers for cycling
F (minimize secondary structures by avoiding long repeats of any base as these cause a DECREASE in available primers for cycling)
G+C content should be at what percent?
40-65%
the final concentration of Mg^2 should be what amount?
0.5 to 5mM
Higher concentration ofMg^2 = ?
Higher concentration ofMg^2 = higher product yield; lower specificity and fidelity
Lower Mg^2 concentration =?
no PCR Product
ideal concentration of dNTPs ?
200μM
Higher dNTP = ?
Higher dNTP = chelates Mg^2–inhibiting DNA polymerase
Lower dNTP = ?
HIGHER Fidelity; lowver/reduced yield