Eukaryotes and Prokaryotes

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The three domain paradigm.

Living organisms are typically divided into three domains: the bacteria, the archaea, and the eukarya (eukaryotes). However, the types of cells fall into just two groups - prokaryotes (including bacteria and archaebacteria) and eukaryote.

There are several differences between prokaryotes and eukaryotes. Prokaryotes lack a membrane around their genetic information, whereas eukaryotes contain their genome within a nuclear membrane within the cell membrane. Eukaryotes further package their DNA into chromosomes, whereas prokaryotes have only a single double-stranded DNA ring and possibly other smaller rings (called plasmids).

There are differences in DNA replication, transcription, and translation between prokaryotes and eukaryotes as well. Noticeably, how replication and transcription are initiated and finished are dependent on the type of cell. Eukaryotes also add two extra steps in transcription/translation: the packaging of the mRNA and the splicing out of introns. (See Introduction to DNA: Eukaryotes-Only Steps for more information.)

Fundamentally, prokaryotes and eukaryotes represent two different paradigms. With some exceptions, the majority of multicellular life is eukaryotic. Said another way, most prokaryotes are single-celled organisms. Competition happens at a fast pace in a single-celled environment. Prokaryotes in general are designed to respond to changes the environment as quickly and efficiently as possible, whereas eukaryotes tend to have longer, more flexible but more tedious pathways.

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