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Cell nucleus
Learning objectives
After completing this study unit, you will be able to:
- Describe the structure and function of the nucleus.
- Explain the role of the nucleolus in cell functions.
- Describe how DNA gets packaged into chromatin.
- Compare chromatin, chromosomes and sister chromatids.
Introduction
The cell nucleus is the command center of the cell. It is usually large, round or oval, and located towards the center of the cell. Some cells can have multiple nuclei (skeletal muscle cells), while others have no nucleus at all (mature erythrocytes).
The nucleus is surrounded by a double-membraned nuclear envelope, with nuclear pores that allow communication between the cytoplasm and the nucleoplasm. The nucleus also contains the nucleolus and dispersed chromatin.
The nucleus stores most of the cell’s genetic material in the form of DNA. It contains machinery necessary for DNA replication and RNA synthesis. The nucleolus is a specialized region within the nucleus that serves as the ribosome factory of the cell.
In non-dividing cells, DNA gets packaged as loosely dispersed threads known as chromatin. Prior to cell division, DNA undergoes replication to ensure equal DNA distribution to daughter cells. During cell division, chromatin condenses to form chromosomes and each chromosome has two sister chromatids. Humans typically have 46 chromosomes in 23 pairs, one chromosome from each pair being inherited from each biological parent. A pair of chromosomes are considered homologous chromosomes.
Explore concepts
Parts of the nucleus
The nucleus is surrounded by the nuclear envelope and contains chromatin and one or more nucleoli.
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:watermark(/images/watermark_only.png,0,0,0):watermark(/logos/logo_url.png,-10,-10,0):format(jpeg)/images/learnable/inner-nuclear-membrane/QbFASS0wTVH86ZppEDirTQ_inner-nuclear-membrane.jpg "Inner nuclear membrane (Membrana nuclearis interna); Image: Paul Kim"){kind=logo}
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:watermark(/images/watermark_only.png,0,0,0):watermark(/logos/logo_url.png,-10,-10,0):format(jpeg)/images/learnable/nucleoplasm/U3xjxvm9hig5qtE0ZlZWg_nucleoplasm.jpg "Nucleoplasm (Nucleoplasma); Image: Paul Kim"){kind=logo}
:watermark(/images/watermark_only.png,0,0,0):watermark(/logos/logo_url.png,-10,-10,0):format(jpeg)/images/learnable/chromatin-1/H4W4zcqG0OdRRodqELaHA_chromatin.jpg "Chromatin (Chromatinum); Image: Paul Kim"){kind=logo}
:watermark(/images/watermark_only.png,0,0,0):watermark(/logos/logo_url.png,-10,-10,0):format(jpeg)/images/learnable/nucleolus-3/x2VRo0HLbduo5JlRjzpIbw_nucleolus.jpg "Nucleolus; Image: Paul Kim"){kind=logo}
Cell nucleus
Nucleus
1/11
Synonyms:
none
Chromatin and chromosomes
DNA along with histone proteins form nucleosomes, which coil and condense to form chromatin fibers.
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Take a quiz
Organize and condense your knowledge of the cell nucleus with this quiz!
Summary
Parts |
Nuclear envelope: surrounds the nucleus, has two membranes |
|---|---|
Functions |
Stores most of the cell’s genetic material (DNA) |
Nucleolus |
Specialized dense region within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are synthesized |
Chromatin |
DNA along with proteins |
Chromosomes |
Condensed form of chromatin in dividing cells |
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