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Bacteria share their DNA

Gene transfer confers on bacteria the capability to accept helpful genes from other microbes. In eukaryotes from algae all the way up to humans, gene transfer occurs by one mechanism, the fusion of gametes. One gamete from a female and one from a male creates a zygote that carries the DNA from both parents. Bacteria and archaea have three major routes whereby they exchange genes: transformation, transduction, and conjugation. All of these methods are called horizontal gene transfer because they occur between two or more adult cells rather than the standard sharing of genes by producing daughter cells.

Transformation occurs when bacteria take in DNA directly from the environment. The DNA may be either the molecule from the nucleoid or a plasmid. In either case, the DNA dissolves in an aqueous environment when a cell dies and lyses. A live bacterial cell encountering the DNA in its habitat may attach to the molecule and use an enzyme to unravel the large polymer. DNA is a double-stranded structure resembling a ladder. The enzyme cuts the ladder’s rungs to separate the DNA in half. One half degrades, but the cell pulls the other half inside where it will incorporate it into its own DNA.


  

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