Home
Not everything that can be counted counts,
and not everything that counts can be counted.
Albert Einstein
Day 3: DNA verification and DNA design
Assignments Due
- Toward reprogramming bacteria with small molecules and RNA, J. Gallivan (Curr Opin Chem Biol 2007, 11:612-619)
- Using movies to analyse gene circuit dynamics in single
cells, J. Locke and M. Elowitz (Nat
Rev Microbiol 2009,
7(5):383-392)
- Primer3 Plus, an enhanced web interface to Primer3, A.
Untergasser et al. (Nucleic Acids Research 2007, 35:
Web Server issue W71-74)
- RibosomalBindingSites.pdf (in OWL-Space Resources)
Discussion
Overview of Experiment
In today's lab, you set up several types of PCR reactions for
the colony screen: the negative control demonstrates
that in the absence of a specific template DNA, the primers
alone do not amplify a specific product; the reactions using
plasmid DNA are for amplification of specific BioBricks; colony
PCR is used to screen putative recombinants after
ligation/transformation. Additionally,
you evaluate the transformations--what evidence do you have
that your genetic circuit is working?
Background
PCR Colony Screen
PCR of an individual bacterial colony is a quick and relatively
easy method to screen transformants. We use forward and reverse
primers that bind upstream and downstream, respectively, of
the multiple cloning site (MCS) on BioBricks or an internal
primer (i.e., one that anneals to the insert DNA) with one of
the MCS primers. The size of the product generated varies with
the insert present in the BioBrick. Thus, any single colony producing
an amplified fragment of the expected size is likely to contain
the desired plasmid DNA. We use
OneTaq® Hot
Start Quick-Load® 2X Master Mix with Standard Buffer to
screen colonies resulting from ligation of BBa_R0040 and BBa_E0840.
Because we are using a "hot start" mix, reactions can be set
up at room temperature.
PCR Reactions:
- Preparation of PCR reactions in the order given in Table
1 minimizes contamination of the stock solutions and the
samples
- A 0.2 or 0.5 ml tube size is required to fit into the thermal
cycler.
Note: Label the tubes on the lids.
- Each column in the table represents a single tube
- Reactions will be performed in 50 µl final volumes
- You will have a TOTAL of 7 PCR reactions: 1 negative
control; 2 using plasmid DNA (diluted 1:100 in nuclease-free
water); 4 with individual bacterial colonies
Table 1: Construction of PCR Reactions. Add
reagents in the order listed here.
PCR Reactions: |
Negative Control (no DNA) |
Plasmid DNA (X2)
|
Bacterial
Colony (X4) |
2X Master Mix |
25 µl |
25 µl |
25 µl |
Nuclease-Free
Water
(NF H2O) |
19 µl
|
19 µl
|
20 µl
|
Forward Primer (1 µM final concentration) |
2.5 µl
VF2
|
2.5 µl
VF2
|
2.5 µl
VF2
|
Reverse Primer (1 µM final concentration) |
2.5 µl
VR
|
2.5 µl
VR
|
2.5 µl
VR
|
DNA Template |
1 µl nuclease-free water
|
1 µl
plasmid DNA (P) (1:100)
|
"touch"
bacterial colony (C)
|
Each team will pick 4 colonies today:
- Set pipette to 3 µl and use a sterile tip to lightly touch a
single colony (do not remove ALL of the colony or gouge the agar!)
Assign an identification symbol to each colony and label the
bottom of the plate under the "spot" -- this plate can be incubated
at 37°C for outgrowth of the individual colonies; you can culture
any "positives" from this plate
- Gently pipet up and down to mix cells with reaction components--the
solution should appear "cloudy"
- After adding all of the reagents, gently tap tubes to
mix
- Take your samples to a thermal cycler (in B05-C.
NOTE: there are only 3 machines; the cycler will be started by the instructor when enough students are ready.
Be certain to record in your notebook the position and labels of your samples and an I.D. of the instrument used.
- Cycling Conditions:
- Cell disruption:
94°C for 10 min
- 30 cycles:
94°C for 30 sec (denaturation)
50°C for 30 sec (annealing)
68°C for 90 sec (extension)
- Final extension:
68
°C for 5 minutes to complete the run
- HOLD at 4°C indefinitely
Annotation of Vector Sequence
Download ApE:
A plasmid Editor and use it to find the following
features in the sequence for BBa_I13522 (see I13522-GFP.docx uploaded
in OWL-Space Resources):
Primer Design
- Each team uses Primer3 or Primer3Plus to
design primers that will mutate a single nucleotide in the ribosomal
binding site (RBS) for production of GFP in BBa_I13522
- Use NEB Tm Calculator to estimate the optimal annealing temperature for PCR: choose "Phusion Hot Start Flex" and "Phusion Hot Start Flex 2X Master Mix"
Copyright, Acknowledgements,
and Intended Use
Created by B. Beason (bbeason@rice.edu), Rice University, 21 November 2007
Updated 31 October 2013