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The most characteristic feature of a eukaryotic cell, the nucleus, consists of a nucleoplasm surrounded by a double nuclear membrane pierced by nuclear pores. The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.

The most characteristic feature of a eukaryotic cell, the nucleus, consists of a nucleoplasm surrounded by a double nuclear membrane pierced by nuclear pores.<ref> http://biotech.icmb.utexas.edu/search/dict-search.html</ref>

The nucleoplasm contains the (linear) chromosomes of the cell, which are organised into heterochromatin, which stains only a little, and euchromatin, which stains more densely. The most important euchromatic area is the nucleolus, in which ribosomes are formed.

#εύ-καρυον (eu-karyon) - true kernel.  

#εύ-καρυον (eu-karyon) - true kernel.  

DNA storage takes up about 10% of the cell of both prokaryotes (nucleoid area) and eukaryotes (nucleus). However, don't forget that some of the genome lives elsewhere: plasmids, endosymbionts (mitochondria), etc. The nucleus of eukaryotes also protects the genome from the cytoskeleton. Condensation of genome during mitosis is required to withstand these stresses. This is not relevant in prokaryotes, as they lack a cytoskeleton. The existence of the nucleus permits processing of mRNA, and therefore defers translation. Alternative splicing can be performed to generate different proteins from the same RNA primary transcript. mRNA is capped and tailed to permit it to exit the nucleus. rRNA and tRNA are also heavily processed by RNA editing, i.e. base modification (this also occurs to some mRNA in trypanosomes). rRNA modification occurs in the nucleolus, where ribosomes are constructed.

DNA storage takes up about 10% of the cell of both prokaryotes (nucleoid area) and eukaryotes (nucleus). However, don't forget that some of the genome lives elsewhere: plasmids, endosymbionts (mitochondria), etc. The nucleus of eukaryotes also protects the genome from the cytoskeleton. Condensation of genome during mitosis is required to withstand these stresses. This is not relevant in prokaryotes, as they lack a cytoskeleton. The existence of the nucleus permits processing of mRNA, and therefore defers translation. Alternative splicing can be performed to generate different proteins from the same RNA primary transcript. mRNA is capped and tailed to permit it to exit the nucleus. rRNA and tRNA are also heavily processed by RNA editing, i.e. base modification (this also occurs to some mRNA in trypanosomes). rRNA modification occurs in the nucleolus, where ribosomes are constructed.

The nucleus is bound by a double-membrane, which is contiguous through the nuclear pores, known as the nuclear envelope. The pores are required to allow RNA out and membrane lipids in (which is needed for growth during S phase).

The nucleus is bound by a double-membrane, which is contiguous through the nuclear pores, known as the nuclear envelope. The pores are required to allow RNA out and membrane lipids in (which is needed for growth during S phase).<ref> Berg, Jeremy M.; Tymoczko, John L.; and Stryer, Lubert."Biochemistry". W. H. Freeman and Co. ; c2002 </ref>

The inner face of the inner nuclear envelope (INE) is coated by the nuclear lamina, which contains intermediate fibres called lamins A, B and C (at least in mammals). Phosphorylation of lamins by kinases cause nuclear envelope breakdown during prometaphase. Chromosomes occupy definite positions within the nucleus because of the interaction between lamins and telomeres, for example the Rabl conformation in yeast.

The inner face of the inner nuclear envelope (INE) is coated by the nuclear lamina, which contains intermediate fibres called lamins A, B and C (at least in mammals). Phosphorylation of lamins by kinases cause nuclear envelope breakdown during prometaphase. Chromosomes occupy definite positions within the nucleus because of the interaction between lamins and telomeres, for example the Rabl conformation in yeast.

 

[[Category:Molecular Biology]]

[[Category:Molecular Biology]]

[[Category:Cellular Biology]]

[[Category:Cellular Biology]]

[[Category:microbiology]]

[[Category:microbiology]]