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Questions and Answers
What is the primary characteristic of heterochromatin?
Which structure is primarily responsible for the formation of rRNA?
Which of the following is NOT a function of the nucleus?
In the electron microscopy of the nucleolus, which area contains mature rRNA?
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What is the composition of the nuclear sap (nucleoplasm)?
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What is the typical number of nuclei in most cells?
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What is the appearance of euchromatin in the nucleus?
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Which component of the nucleus is responsible for the formation of nuclear pores?
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Which of the following statements about the nuclear envelope is true?
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Which shape is NOT associated with the nucleus?
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Study Notes
Heterochromatin
- Dark staining, inactive chromatin.
- Tightly coiled with inactive genes.
- Types:
- Peripheral chromatin: Attached to the inner nuclear membrane.
- Chromatin islets.
- Nucleolus associated chromatin: Attached to the nucleolus.
Nucleolus
- Darkly basophilic mass within the nucleus when viewed under light microscopy.
- Under electron microscopy, shows a dark area with:
- Pars amorpha: Contains filaments of DNA.
- Pars fibrosa: Newly formed rRNA.
- Pars granulosa: Mature rRNA.
- Also contains a light area called the nucleolar sap.
- Functions in the formation of rRNA.
Nuclear Sap (Nucleoplasm)
- Jelly-like, amorphous substance.
- Fills spaces between chromatin.
- Composed of nucleoproteins, enzymes, and metabolites.
- Provides a medium for the transport of RNA and nucleoproteins.
Functions of the Nucleus
- Controls all vital functions of the cell.
- Controls cell division.
- Carries genetic information (heredity).
- Forms the three types of RNA.
Nucleus under Light Microscopy (LM)
- Stains basophilic due to the presence of DNA.
- Appearance can be pale or vesicular (active) or dark (less active).
- Usually, cells have one nucleus (mononucleated), but some can have two (binucleated) or many (multinucleated).
- Shape can be rounded, oval, flat, bilobed, or lobulated.
- Location can be central, eccentric, basal, or peripheral.
Nucleus under Electron Microscopy (EM)
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Nuclear Envelope:
- Outer membrane: Ribosomes attached to it, continuous with the rough endoplasmic reticulum (rER).
- Inner membrane: Attached to peripheral chromatin.
- Perinuclear space: Located between the inner and outer membranes.
- Nuclear pores: Where the inner and outer membranes fuse. Composed of octagonal rings formed of nucleoporins. Filaments extending into the cytoplasm and nucleus.
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Nuclear Chromatin (DNA):
- Euchromatin: Pale staining, active. Extended chromatin with active genes.
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Description
Explore the intricate details of the nucleus, heterochromatin, and nucleolus through this quiz. Learn about the structural components and functions associated with the nucleus, including its role in controlling cell functions and genetic information. Perfect for students of cell biology and genetics.
