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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.
The nuclear matrix is also believed to be contained in the nucleoplasm where it functions to maintain the size and shape of the nucleus, in a role similar to that of the cytoskeleton found in the cytoplasm. [10] However, the existence and the exact function of the nuclear matrix remain unclear and heavily debated.
Cells are broadly categorized into two types: eukaryotic cells, which possess a nucleus, and prokaryotic cells, which lack a nucleus but have a nucleoid region. Prokaryotes are single-celled organisms such as bacteria , whereas eukaryotes can be either single-celled, such as amoebae , or multicellular , such as some algae , plants , animals ...
DNA gyrase also has topoisomerase type II activity; thus, with it being a homologue of topoisomerase IV (also having topoisomerase II activity) we expect similarity in the two proteins' functions. DNA gyrase's preliminary role is to introduce negative super coils into DNA, thereby relaxing positive supercoils that form during DNA replication.
The cell nucleus (from Latin nucleus or nuculeus 'kernel, seed'; pl.: nuclei) is a membrane-bound organelle found in eukaryotic cells.Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many.
The prototypical examples are nucleosomes, complexes in which genomic DNA is wrapped around clusters of eight histone proteins in eukaryotic cell nuclei to form chromatin. Protamines replace histones during spermatogenesis.
Multiple forms of extrachromosomal DNA exist, and, while some of these serve important biological functions, [1] they can also play a role in diseases such as cancer. [ 2 ] [ 3 ] [ 4 ] In prokaryotes , nonviral extrachromosomal DNA is primarily found in plasmids , whereas, in eukaryotes extrachromosomal DNA is primarily found in organelles . [ 1 ]
For example, lipid groups can play an important role in increasing molecular hydrophobicity. This allows for the interaction of proteins with cellular membranes and protein domains . [ 4 ] In a dynamic role [ clarification needed ] , lipidation can sequester a protein away from its substrate to inactivate the protein and then activate it by ...