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Genetic Recombination and Horizontal Gene Transfer

Genetic recombination is the exchange of genes between DNA molecules, contributing to genetic diversity alongside mutations. Learn about vertical and horizontal gene transfer mechanisms like transformation, transduction, and conjugation, which transfer genes between generations and cells. Explore the types of plasmids involved and the significance of these processes in genetic evolution.

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Genetic Recombination and Horizontal Gene Transfer

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  1. Genetic Recombination • Exchange of genes between two DNA molecules • Forms new combination of genes on a chromosome • Along with mutations, contributes to genetic diversity

  2. Types of Genetic Transfer • Vertical gene transfer • Horizontal gene transfer • Occurs during reproduction, between generations of cells • Transfer of genes between cells of the same generation

  3. Mechanisms of Horizontal Transfer • Genes are naturally transferred between bacteria using three mechanisms • Transformation • Transduction • Conjugation • All result in recombination

  4. Transformation • Transfer of naked DNA from one bacterium to another • Works best when donor and receipt are closely related • Discovered by Fredrick Griffith in 1928 while working with Streptococcus pneumoniae

  5. Griffith Experiment

  6. Avery, MacLeod and McCarty • Showed DNA was transforming agent • Competent cells pick up DNA and integrate it into chromosome

  7. Transduction • Bacterial DNA transferred from donor to recipient via bacteriophage • Two types of transduction • Generalized • Specialized

  8. Transduction

  9. Conjugation • Requires direct contact between cells • Only form of gene exchange in which donor survives • Mediated by plasmids • Can code for traits that give bacteria advantage

  10. Plasmid Types • Fertility factor • Dissimilation plasmids • Resistance factor • Bacteriocin factor • Virulence plasmids

  11. Conjugation

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