Organelle · double membrane
Nucleus
The control centre
In view
Each colour marks one pair of chromosomes, each copy in its own territory, as in chromosome-painting microscopy. The darker, thicker stretches are heterochromatin, lining the envelope and the nucleolus. This cell is female (XX): one X is shut down and packed into the dense Barr body against the envelope. RNA and ribosome parts stream out through the pores and proteins stream in.
The nucleus holds the genome: about 6.3 billion DNA letters that would stretch 2 metres end to end, packed into a sphere 5–10 µm across. More than a third of it lies in silent, tightly packed stretches (heterochromatin) held against the nuclear lamina, a thin mesh of lamin filaments lining the inside.
Two membranes wrap it, pierced by thousands of pores. Each pore is a ring of about 30 kinds of protein that joins the two membranes, with a basket on its inner side. Inside, the cell decides which genes are copied into RNA, and therefore what it becomes and does.
- Diameter
- 5–10 µm
- DNA
- ≈ 2 m · 6.3 billion bp
- Chromosomes
- 46
- Nuclear pores (HeLa)
- ≈ 2,800
Did you know?
The DNA is about 270,000 times longer than the nucleus is wide. That is like stuffing 18 km of fishing line into a tennis ball.
Sources
- Chromosome territories · Cremer & Cremer 2010 · Cold Spring Harb Perspect Biol
- Kinetic analysis of translocation through nuclear pore complexes · Ribbeck & Görlich 2001 · EMBO J
- Lamina-associated domains: links with chromosome architecture, heterochromatin, and gene repression · van Steensel & Belmont 2017 · Cell
- Nucleolar organizer regions: genomic 'dark matter' requiring illumination · McStay 2016 · Genes Dev
- A morphological distinction between neurones of the male and female, and the behaviour of the nucleolar satellite during accelerated nucleoprotein synthesis · Barr & Bertram 1949 · Nature
- Structural aspects of the inactive X chromosome · Bonora & Disteche 2017 · Phil Trans R Soc B
- On the length, weight and GC content of the human genome · Piovesan et al. 2019 · BMC Res Notes
- Nuclear diameter · BioNumbers · BNID 100440
- The molecular architecture of lamins in somatic cells · Turgay et al. 2017 · Nature
- How big is the endoplasmic reticulum of cells? · Milo & Phillips · Cell Biology by the Numbers
- The cellular environment shapes the nuclear pore complex architecture · Schuller et al. 2021 · Nature
- The nuclear pore complex: understanding its function through structural insight · Beck & Hurt 2017 · Nat Rev Mol Cell Biol
- Nucleoporins as components of the nuclear pore complex core structure and Tpr as the architectural element of the nuclear basket · Krull et al. 2004 · Mol Biol Cell
- 4.3 Eukaryotic Cells · OpenStax · Biology 2e
- How many chromosomes do people have? · MedlinePlus Genetics (NIH)