Ethics, Safety, and Future Directions
What bacteria are generally more resistant to disinfectants than Gram (+) bacteria due to their outer membrane?
Gram (-) bacteria
What is horizontal gene transfer, and how does it differ from vertical gene transfer?
Horizontal gene transfer exchanges genes between cells of the same generation, while vertical transfer passes genes to offspring during reproduction.
What enzyme is essential for covalently linking DNA fragments after restriction enzyme digestion?
DNA ligase seals the sugar-phosphate backbones of DNA fragments.
What is the purpose of polymerase chain reaction (PCR) in biotechnology?
PCR amplifies specific DNA sequences exponentially using heat-stable DNA polymerase.
What is one medical application of recombinant DNA technology?
rDNA technology allows the production of human insulin in bacterial systems for diabetes treatment.
Which microbe is the most resistant to disinfection and even autoclaving?
Prions
What experimental evidence first demonstrated transformation in bacteria?
Frederick Griffith’s experiment showing that nonpathogenic Streptococcus pneumoniae became virulent after exposure to heat-killed pathogenic bacteria.
Why are sticky ends produced by restriction enzymes advantageous in rDNA technology?
Sticky ends allow complementary base pairing between DNA fragments from different sources, enhancing recombination efficiency.
How does electroporation aid in introducing foreign DNA into cells?
Electroporation creates temporary pores in the cell membrane using electrical pulses, allowing DNA to enter.
How does gene therapy aim to treat genetic disorders?
Gene therapy introduces functional genes to replace defective ones, restoring normal cellular function.
Which microbial form can survive desiccation due to its protective coat?
Endospores
How does conjugation differ between F⁺ × F⁻ and Hfr × F⁻ mating pairs in bacteria?
In F⁺ × F⁻, the recipient becomes F⁺; in Hfr × F⁻, chromosomal genes (not the entire F factor) are transferred, usually leaving the recipient F⁻ but recombinant.
What is the role of the Ti plasmid in plant genetic engineering?
The Ti plasmid from Agrobacterium tumefaciens is used as a vector to introduce foreign genes into plant genomes.
Why is reverse transcriptase crucial for creating cDNA libraries?
Reverse transcriptase synthesizes complementary DNA from mRNA, allowing cloning of expressed genes without introns.
How are DNA vaccines different from traditional vaccines?
DNA vaccines introduce plasmids encoding antigens, allowing host cells to produce the antigen internally and trigger an immune response.
Which two microbial structures make nonenveloped viruses more resistant than enveloped ones?
Protein capsid and lack of lipid envelope
What is the difference between generalized and specialized transduction?
Generalized transduction - any bacterial gene can be transferred by a lytic phage
Specialized transduction - only specific genes near the prophage integration stie and transferred by a lysogenic phage
Why might E. coli not always be the best organism for producing eukaryotic proteins?
E. coli lacks post-translational modification systems required for proper folding and glycosylation of eukaryotic proteins.
How does blue-white screening differentiate recombinant bacteria?
Recombinant colonies appear white because insertion of foreign DNA disrupts the β-galactosidase gene, preventing X-gal hydrolysis.
How do forensic microbiologists use DNA fingerprinting?
DNA fingerprinting analyzes unique genetic markers to identify individuals or microbial sources in investigations.
Which test evaluates bacterial survival in the manufacturer’s recommended dilution of a disinfectant?
Use-dilution test
How do plasmids and transposons contribute to bacterial evolution and antibiotics resistance?
Plasmids carry resistance (R) genes that can be shared between species via conjugation, while transposons can move these genes between chromosomes or plasmids, spreading resistance traits.
How does site-directed mutagenesis differ from random mutagenesis?
Site-directed mutagenesis introduces targeted base changes to alter specific amino acids, whereas random mutagenesis introduces unpredictable changes across the genome.
Why is the Taq polymerase enzyme specifically used in PCR?
Taq polymerase from Thermus aquaticus withstands high denaturation temperatures required during PCR cycles.
Why might antisense RNA be used in agricultural biotechnology?
Antisense RNA binds to complementary mRNA sequences, blocking translation and silencing unwanted gene expression.