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Being a universal eukaryotic property, mitosis probably arose at the base of the eukaryotic tree. As mitosis is less complex than meiosis, meiosis may have arisen after mitosis. [93] However, sexual reproduction involving meiosis is also a primitive characteristic of eukaryotes. [94] Thus meiosis and mitosis may both have evolved, in parallel ...
The 2006 Nobel Prize in Chemistry was awarded to Roger D. Kornberg for creating detailed molecular images of RNA polymerase during various stages of the transcription process. [3] [4] In most prokaryotes, a single RNA polymerase species transcribes all types of RNA.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
The 3'-5' action of DNA polymerase along the parent strand leaves a short single-stranded DNA (ssDNA) region at the 3' end of the parent strand when the Okazaki fragments have been repaired. Since replication occurs in opposite directions at opposite ends of parent chromosomes, each strand is a lagging strand at one end.
RNA polymerase is composed of a core and a holoenzyme structure. The core enzymes contains the catalytic properties of RNA polymerase and is made up of ββ′α2ω subunits. This sequence is conserved across all bacterial species. The holoenzyme is composed of a specific component known as the sigma factor (σ-factor). The sigma factor ...
Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis). The thick lines are chromosomes, and the thin blue lines are fibers pulling on the chromosomes and pushing the ends of the cell apart. The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3.
All three eukaryotic polymerases have five core subunits that exhibit homology with the β, β’, α I, α II, and ω subunits of E. coli RNA polymerase. An identical ω-like subunit (RBP6) is used by all three eukaryotic polymerases, while the same α-like subunits are used by Pol I and III.
In eukaryote cells, RNA polymerase III (also called Pol III) is a protein that transcribes DNA to synthesize 5S ribosomal RNA, tRNA, and other small RNAs. The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose expression is required in all cell types and most environmental conditions.