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#gene transfer

21 public questions tagged with this topic.

ZOOLOGY

Which of the following is NOT a method of gene transfer?

Electrophoresis is used for DNA separation, not gene transfer. Microinjection, biolistics, and heat shock transformation are gene transfer methods. This follows from NCERT principle where relation explains outcome clearly for students.

Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Biology - Zoology portion covering relevant system and function, Topic: Structural organization and physiology.

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Transgenic Plant -1

Trypsin inhibitor gene transferred to tobacco was sourced from:

Search for effective protease inhibitor for transgenic resistance identified cowpea trypsin inhibitor as potent candidate due to broad activity against lepidopteran gut proteases and stability in alkaline environment. Cowpea Vigna unguiculata seeds accumulate defense proteins to protect against storage pests. Gene CpTI encoding 80 amino acid inhibitor with two disulfide bridges isolated from developing seeds and placed under CaMV 35S promoter. Tobacco transformed with CpTI exhibited 2 to 5 percent soluble protein as inhibitor, reducing tryptic activity of Heliothis virescens midgut extracts and causing 50 percent reduction in larval weight gain in feeding bioassays. Compared to soybean Kunitz inhibitor, CpTI showed enhanced resistance to proteolytic degradation due to compact structure. Field trials of transgenic tobacco and later cotton combining CpTI with cry1Ab demonstrated reduced bollworm damage. Hence cowpea provides source of trypsin inhibitor gene utilized in early proteinase inhibitor mediated insect control strategies complementing Bacillus thuringiensis approach in transgenic plant development history. Development involved Agrobacterium mediated transformation with nptII marker and analysis of T1 progeny for Mendelian segregation of inhibitor activity. Resistance level correlated with inhibitor expression dose, illustrating quantitative relationship between defensive protein accumulation and insect growth inhibition in transgenic tobacco lines.

Ref: Hilder Nature 1987 CpTI cowpea tobacco; Gatehouse Plant Mol Biol 1993 Vigna; NCBI NBK131103; PubMed 3033487 cowpea trypsin inhibitor source.

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Transgenic Plant -1

Superweeds may arise due to transfer of genes conferring:

Superweeds describe weedy populations that have acquired herbicide resistance via gene flow from cultivated crops, making control challenging. When transgenic crop expressing bar gene for glufosinate tolerance or cp4-epsps for glyphosate tolerance cross-pollinates with sexually compatible weed such as Brassica rapa, hybrid offspring inherit resistance allowing survival under herbicide application. Repeated selection in fields sprayed with same herbicide enriches resistant allele frequency, and backcrossing to weed parent restores weediness while retaining transgene. Documented cases include glyphosate-resistant canola volunteers and bentgrass. Resistance to insects does not provide similar advantage because herbivory rarely limits weed growth in cropped fields where competition decisive. Therefore concern about superweeds specifically links to herbicide resistance gene transfer, driving implementation of management practices like crop rotation, herbicide mode action rotation, and containment via chloroplast transformation or male sterility to reduce pollen-mediated gene escape. Population genetics model predicts rapid increase of resistance allele when selection pressure continuous, especially if herbicide applied annually over large area. Volunteer canola plants carrying transgene found outside fields illustrate escape potential. Management includes rotating herbicide modes of action, using multiple herbicide tolerant traits, and deploying crops with male sterility or chloroplast transformation. Understanding herbicide resistance transfer to weeds informs stewardship guidelines

Ref: Snow Am J Bot 1997 superweeds; Ellstrand Bioscience 2001; NCBI NBK131103; ISAAA superweed brief 2020; https://www.isaaa.org/

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Microbial Physiology

Antibiotic resistance genes are commonly transferred between bacteria via:

Vertical inheritance through binary fission faithfully copies the single circular chromosomal DNA with high fidelity via DNA polymerase III holoenzyme but fails to explain extraordinarily rapid global dissemination of antibiotic resistance observed within decades of antibiotic introduction. Horizontal gene transfer provides direct mechanism for movement of accessory genes between genetically unrelated cells, even across genus barriers. Conjugation involves direct cell-to-cell contact via retractile sex pilus encoded by tra operon and transfer of conjugative plasmids and integrative conjugative elements carrying resistance cassettes through type IV secretion system. Transformation allows uptake of naked extracellular DNA from environment via natural competence machinery ComEA and ComEC in species like Streptococcus pneumoniae, Bacillus subtilis and Neisseria gonorrhoeae. Generalized and specialized transduction uses temperate bacteriophages that mistakenly package host DNA including resistance genes during lytic cycle and inject into recipient, as documented for transfer of mecA. Together these mechanisms allow mobilization of beta-lactamases blaCTX-M, carbapenemases blaKPC and blaNDM, erm methylases, tet and van operons across species and diverse habitats within hours, far outpacing mutation. Passive diffusion of small molecules and flagellar swimming motility do not transfer genetic information, distinguishing HGT as the primary driver of resistance pan-genome expansion and public health crisis.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: Horizontal Gene Transfer and Resistance Spread.

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