CHAPTER 5 BACTERIAL TRANSFORMATION & POLYMERASE CHAIN REACTION

By john wesley kelly the third

What is the clinical significance of bacterial transformation?

The ability of bacteria to gain new traits such as antibiotic resistance from free DNA affects treatment and disease progression.

Why is it critical to understand bacterial transformation in biotechnology?

It is the basis of cloning and recombinant DNA work where foreign DNA is introduced into bacteria to produce proteins or study genes.

How did the mouse die in station 1?

It was injected with live virulent S

What did the S

strain contain?

How was the R

strain different from the S

What happened in station 3 of Griffith's experiment?

Heat

What happened in station 4?

The mouse died when given live R

How did the bacteria demonstrate genetic variation?

R cells acquired capsule genes from dead S cells and became virulent S cells.

What happens during DNA release and uptake in the transformation process?

Donor cells lyse and release DNA, and competent recipient cells take up DNA fragments.

What happens during DNA integration?

Incoming DNA recombines with homologous regions of the chromosome.

What happens during bacterial division in the transformation process?

The new DNA is replicated and passed to daughter cells.

What is the clinical significance of bacterial conjugation?

It spreads plasmids carrying antibiotic resistance and virulence genes.

What are the different bacterial mating types?

F⁺, F⁻, Hfr, and F′.

What is the fertility factor?

A plasmid that encodes genes for pilus formation and DNA transfer.

What is the conjugation bridge?

A physical connection through which DNA is transferred from donor to recipient.

How are genes transferred during conjugation?

A single DNA strand is nicked, transferred, and replicated in both cells.

What is high frequency recombination?

When the F factor integrates into the chromosome, causing chromosomal genes to transfer at high frequency.

What is bacterial transduction?

Gene transfer mediated by bacteriophages that accidentally package bacterial DNA.

What happens during bacteriophage attachment?

The phage binds bacterial receptors and injects its nucleic acid.

What happens during phage DNA replication?

The phage genome replicates and phage proteins are produced.

What happens during packaging and phage release?

Phage DNA or bacterial DNA is packaged into capsids and the cell lyses to release phages.

What are the steps of generalized transduction?

Lytic infection, host DNA fragmentation, random DNA packaging, infection of new cells, recombination.

What happens during prophage integration and excision?

Phage DNA integrates into the chromosome and may later excise, sometimes carrying bacterial genes.

What is hybrid DNA formation?

Recombinant DNA containing both donor and recipient sequences.

How is DNA transferred to recipient?

By phage injection in transduction, by a conjugation bridge in conjugation, or by uptake from the environment in transformation.

What is the preintegration state?

before integration

What is the postintegration state

after intergration

What is the clinical significance of bacterial transduction?

It spreads toxin genes and antibiotic resistance, affecting virulence and treatment strategies.

How did genetic engineering revolutionize medicine?

It enabled the creation of insulin, vaccines, growth hormones, gene therapies, and targeted treatments by allowing scientists to directly modify DNA.

What is the donor plasmid?

A circular DNA molecule that carries the gene of interest to be inserted into a host cell.

What are restriction enzymes?

Proteins that cut DNA at specific sequences, creating fragments with predictable ends.

What are DNA ligases?

Enzymes that join DNA fragments together by sealing sugar‑phosphate backbones.

Where do foreign DNA come from?

It can come from any organism whose gene is being inserted, such as human, bacterial, viral, or plant DNA.

What is a chimera?

A recombinant DNA molecule made by combining DNA from two different sources.

What does CaCl₂ solution do to cells?

It makes bacterial cell membranes more permeable so they can take up plasmid DNA.

How does the host bacteria reproduce quickly?

By binary fission, allowing rapid copying of plasmids and recombinant genes.

How can recombinant proteins be used?

They can be used as medicines, vaccines, enzymes, hormones, and research tools.

How did PCR revolutionize medicine?

It allowed rapid DNA amplification for diagnostics, forensics, genetic testing, and pathogen detection.

What are primers?

Short DNA sequences that provide starting points for DNA polymerase during PCR.

What are dNTPs?

The nucleotide building blocks used to synthesize new DNA strands.

What is Taq DNA polymerase?

A heat‑resistant enzyme from Thermus aquaticus that builds DNA during PCR cycles.

What are the three steps of PCR?

Denaturation, annealing, and elongation.

What temp does denaturation occur at?

Around 94–98°C.

What happens during the denaturation phase?

Double‑stranded DNA separates into single strands.

What temp does annealing happen?

Typically 50–65°C depending on primer sequences.

What happens during annealing phase?

Primers bind to their complementary DNA sequences.

What temp does elongation happen at?

Around 72°C, the optimal temperature for Taq polymerase.

What occurs during elongation stage?

Taq polymerase extends primers and synthesizes new DNA strands.

How does PCR multiply? (mathematical formula)

It amplifies DNA exponentially following the pattern 2ⁿ, where n is the number of cycles.

How many cycles of PCR are typical?

Usually 25–35 cycles.