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Prokaryotes have simple cell skeletons. These are highly diverse, and contain homologues of the eukaryote proteins actin and tubulin. The cytoskeleton provides the capability for movement within the cell. [7] Most prokaryotes are between 1 and 10 μm, but they vary in size from 0.2 μm in Thermodiscus spp. and Mycoplasma genitalium to 750 μm ...
Prokaryotic cells have entirely different structures for organizing their DNA (the prokaryotic chromosome equivalent is called a genophore and is localized within the nucleoid region). The overall structure of the chromatin network further depends on the stage of the cell cycle .
Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes, this structure involves DNA binding to a complex of small basic proteins called histones, while in prokaryotes multiple types of proteins are involved.
The nucleoid (meaning nucleus-like) is an irregularly shaped region within the prokaryotic cell that contains all or most of the genetic material. [1] [2] [3] The chromosome of a typical prokaryote is circular, and its length is very large compared to the cell dimensions, so it needs to be compacted in order to fit.
Higher-order packaging is accomplished by specialized proteins that bind and fold the DNA. This generates a series of loops and coils that provide increasingly higher levels of organization and prevent the DNA from becoming tangled and unmanageable. [4] This complex of DNA and proteins are called chromatin. [5]
The two unwound single strands of DNA serve as templates for DNA polymerase, which moves with the helicase (together with other proteins) to synthesise a complementary copy of each strand. In this way, two identical copies of the original DNA are created.
Single-stranded DNA is highly unstable and can form hydrogen bonds with itself that are referred to as 'hairpins' (or the single strand can improperly bond to the other single strand). To counteract this instability, single-strand binding proteins (SSB in prokaryotes and Replication protein A in eukaryotes) bind to the exposed bases to prevent ...
The eukaryotic pre-RC is the most complex and highly regulated pre-RC. In most eukaryotes it is composed of six ORC proteins (ORC1-6), Cdc6, Cdt1, and a heterohexamer of the six MCM proteins (MCM2-7). The MCM heterohexamer arguably arose via MCM gene duplication events and subsequent divergent evolution.