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Horizontal gene transfer
- 1. Section 26.5: HorizontalGene Transfer By Monica Macaro
- 2. Learning Objectives Explainwhy horizontal gene transfer can complicate evolutionary hypothesis Explain why the "Tree of Life" is being replaced by the "Web of Life"
- 3. Horizontal Gene Transfer Process in which an organism incorporates genetic material from another organism without being its offspring Common in bacteria and archaea, rare in eukaryotic cells Genetic information transferred via conjugation, transduction, and transformation Conjugation Transduction Transformatio n
- 4. Horizontal Gene Transferin Eukaryotes Not well understood Hard to detect Frequency and importance in multicellular eukaryotes hard to evaluate Rare due to sexual reproduction and multicellularity More common in certain unicellular eukaryotes (e.g protists) HGT genes only transferred to offspring in multicellular eukaryotes if recipient was a gamete/germ cell
- 5. Eukaryote mayingest bacterial cell via endocytosis and incorporate a bacterial gene Bacterial gene may escape degradation Gene incorporated into genome via nonhomologous recombination Genes may be transferred via viruses Viral DNA incorporated into recipient's DNA About 8% of human genome originates from viruses
- 6. Horizontal Gene Transferin Eukaryote
- 7. Horizontal Gene Transferand Evolution Evolutionary hypothesis focuses on vertical evolution (changes in species due to descent from common ancestor) Genes can be transferred between species via HGT New genes may benefit/hinder organism’s chance for survival May foster evolutionary change
- 8. HGT mayhave been prevalent during life’s early stages Common ancestor may have been a community of cell lineage evolving as a whole rather than a single cell lineage Muddles concept of monophyletic groups “Web of Life” instead of “Tree of Life” HGT indicated by horizontal connections
- 9. The Web ofLife