Domains of Life; Prokaryotic vs. Eukaryotic Cells

ID #2369

I have two questions. One regarding horizontal gene transfer and the second regarding "other genes [that] have been analyzed using comparative methods" (quoted part directly from lecture slide). (1) Were different trees drawn because other researchers looked at data from molecules besides rRNA or a different part of the rRNA that Carl Woese studied? (2) Is horizontal gene transfer temporary? Meaning, are the genes and/or DNA acquired during horizontal gene transfer used only for a specific period and then lost? Or during the sharing does the species then have the ability to make said genes or DNA permanently?

Good questions! To answer your first question, yes, if different genes (besides the 16S rRNA)are compared between organisms then different trees can be drawn due to horizontal gene transfer. This is because one gene might be exchanged between Organism A and Organism B, but a different gene might be exchanged between Organism A and Organism X. To answer your second question, whether or not a transferred gene is retained really depends. Some genes are carried on special circular pieces of DNA called plasmids (which you will learn about at the end of the semester) and plasmids can be transferred between different species of bacteria. Bacteria that gain plasmids don't always keep them. Other genes that are transferred are kept permanently. This commonly happens when antibiotic resistance genes are transferred from one organism to another. 

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