Horizontal Gene Transfer and Endosymbiosis

This page delves deeper into the mechanisms of horizontal gene transfer in bacteria and introduces the concept of endosymbiosis in eukaryotic evolution.

The diagram illustrates the process of horizontal gene transfer in bacteria, specifically focusing on plasmid transfer:

1. A bacterial chromosome and a plasmid are shown.
2. The plasmid replicates and transfers to another bacterium.
3. The recipient bacterium acquires the plasmid, gaining new genetic material.

Definition: A plasmid is a small, circular DNA molecule that can replicate independently of the bacterial chromosome and often carries genes beneficial to the host bacterium.

The page also presents a phylogenetic network, demonstrating the complex relationships between organisms due to both vertical and horizontal gene transfers.

Highlight: The phylogenetic network shows that while vertical gene transfer is predominant for genes related to sexual reproduction, other genes can be transferred horizontally between different lineages.

Endosymbiosis of organelles is mentioned as another crucial mechanism in the evolution of eukaryotic cells.

Vocabulary: Endosymbiosis refers to the process where one organism lives inside another in a mutually beneficial relationship, leading to the evolution of organelles like mitochondria and chloroplasts in eukaryotic cells.

This page emphasizes the importance of both vertical and horizontal gene transfers in shaping the complexity and diversity of genomes across different domains of life.

Example: The acquisition of antibiotic resistance genes by pathogenic bacteria through horizontal gene transfer is a significant concern in modern medicine.