Lab 6 - 7 (hahaha)

What is transformation of ligation?

Introduction of ligation (recombinant DNA) into E. coli

How is transformation of ligation done?

1. Add ligation product to competent cells

2. Incubate on ice (30 min) → DNA binds

3. Heat shock at 42°C (45 sec) → DNA enters cells

4. Return to ice

5. Add nutrient broth and recover at 37°C (~1 hr)

6. Plate on selective media (Amp, Kan, Amp+Kan)

Why is transformation of ligation done?

• To introduce and propagate recombinant plasmid (pAK)

• To identify cells that successfully took up the recombinant DNA

What parameters must be considered for maximum efficiency in transformation of ligation?

Key parameters affecting efficiency:

• Competency of cells (DH5α)

• Quality of ligation product

• Heat shock timing and temperature

• Recovery time

• Antibiotic selection

How will you interpret the results observed on single antibiotic plates versus dual antibiotic plates?

Interpretation summary:

• Growth on Amp only → non-recombinant (vector only)

• Growth on Kan only → possible insert or contamination

• Growth on Amp + Kan → true recombinant clone

• No growth → failed transformation

How will you troubleshoot if you have zero colonies?

• Check competency of cells

• Verify ligation worked

• Confirm antibiotics are correct

• Repeat transformation with controls

How will you troubleshoot if you have a lawn?

• Check antibiotic plates

• Use proper concentrations

• Plate smaller volume

• Ensure sterile technique

What are the possible causes when you have zero colonies and what do the results indicate?

What it indicates:

• Transformation failed

Possible causes:

• Cells not competent

• DNA degraded or not ligated

• Incorrect antibiotic (too strong or wrong plate)

• Heat shock done incorrectly

• No recovery time

What are the possible causes when you have a lawn and what do the results indicate?

What it indicates:

• Too many cells grew → no proper selection

Possible causes:

• No antibiotic in plate

• Antibiotic degraded

• Too much DNA or cells plated

• Contamination

If you do observe positive clones in your next lab (AGE), what other means can you utilize to confirm the positive clones?

1. Antibiotic selection

• Growth on Amp + Kan plates

• Confirms presence of both resistance genes

2. Additional restriction digests

• Use different enzyme combinations

• Compare fragment patterns to expected map

3. PCR (Polymerase Chain Reaction)

• Amplify inserted gene

• Confirms presence and size of insert

4. DNA sequencing

• Determines exact nucleotide sequence

• Confirms:

• Correct insert

• Correct orientation (no flipping)

5. Colony PCR

• Quick screening directly from colonies

• Confirms recombinant without full plasmid prep

What are the steps involved in isolating recombinant clones?

Steps:

1. Pellet bacterial cells (centrifugation)

2. Resuspend in solution 1 (P1)

3. Lyse cells with solution 2 (P2)

4. Neutralize with solution 3 (P3)

5. Centrifuge → remove debris

6. Transfer supernatant to Qiagen column

7. Wash column

8. Elute purified plasmid DNA (pAK)

What is the function of each reagent used in isolating recombinant clones?

• P1: Resuspends cells, contains RNase

• P2: NaOH + detergent → lyses cells, denatures DNA

• P3: Neutralizes → chromosomal DNA + proteins precipitate

• Column (silica): binds DNA in high salt

• Wash: removes contaminants

• Elution (T): releases DNA in low salt

What was the goal in isolating recombinant clones?

Isolate recombinant plasmid (pAK) from transformed cells

How was RE digestion set-up?

• Use ~500 ng plasmid DNA

• Add:

• Buffer

• Restriction enzymes (BamHI, HindIII)

• Water

• Total volume ~15 µL

• Incubate at 37°C (overnight)

What is the purpose of RE digestion?

• Cut recombinant plasmid at specific sites

• Generate fragments for analysis on gel

How do RE digestion work?

• REs recognize specific sequences

• Produce sticky ends

• Used to confirm plasmid structure (restriction map)