Cell Ultrastructure: The Nucleus

• Nuclear Envelope: Outer membrane continuous with rough endoplasmic reticulum, inner membrane anchored to nuclear lamina.

• Nuclear Lamina: Protein filament meshwork adjacent to inner membrane, provides support and shapes nuclear envelope, aids in positioning of nuclear pores.

• Nuclear Pore: Thousands present, octagonal structure with a ring-like arrangement called a pore complex, allows transport of water-soluble molecules across the nuclear envelope.

• Nucleoplasm: Highly viscous liquid in nucleus, contains nucleotides and enzymes, network of fibers called nuclear matrix present.

• Chromatin: Threads and fibers in nucleoplasm when cell not dividing, comes in two types: euchromatin (relatively dispersed, DNA transcribed) and heterochromatin (condensed, DNA not transcribed).

• Nucleosome: Basic unit of chromatin, DNA coiled around a protein unit called a histone.

• Chromatin Packing: Chromatin undergoes several levels of coiling to form a chromosome.

• Nuclear Matrix: Fiber network in nucleoplasm, similar to cell cytoskeleton.

• Chromosomes: Chromatin fibers condense and form chromosomes visible during cell division.

• Nucleolus: Dense basophilic material in nucleoplasm, not enclosed by a membrane, contains instructions to make ribosomal RNA.

• Ribosomes: Consist of equal parts ribosomal RNA and proteins, closely connected with protein synthesis.

• Chromosome Complement: Describes number, size, and morphology of chromosomes in an individual or species.

• Karyotype: Describes chromosome complement in terms of number, size, and morphology.

• Nuclear Division: Chromatin fibers condense and form chromosomes during cell division, nucleolus disappears and reappears post-division.

• Trisomy and Monosomy: Conditions resulting in an abnormal number of chromosomes.

• Chromosome Numbers: Each species has a characteristic number of chromosomes.

• Ribosomal RNA Production: In the nucleolus, chromosomal DNA transcribes ribosomal RNA, which then associates with proteins to form ribosomal particles.

• Nuclear Envelope: Outer membrane continuous with rough endoplasmic reticulum, inner membrane anchored to nuclear lamina.

• Nuclear Lamina: Protein filament meshwork adjacent to inner membrane, provides support and shapes nuclear envelope, aids in positioning of nuclear pores.

• Nuclear Pore: Thousands present, octagonal structure with a ring-like arrangement called a pore complex, allows transport of water-soluble molecules across the nuclear envelope.

• Nucleoplasm: Highly viscous liquid in nucleus, contains nucleotides and enzymes, network of fibers called nuclear matrix present.

• Chromatin: Threads and fibers in nucleoplasm when cell not dividing, comes in two types: euchromatin (relatively dispersed, DNA transcribed) and heterochromatin (condensed, DNA not transcribed).

• Nucleosome: Basic unit of chromatin, DNA coiled around a protein unit called a histone.

• Chromatin Packing: Chromatin undergoes several levels of coiling to form a chromosome.

• Nuclear Matrix: Fiber network in nucleoplasm, similar to cell cytoskeleton.

• Chromosomes: Chromatin fibers condense and form chromosomes visible during cell division.

• Nucleolus: Dense basophilic material in nucleoplasm, not enclosed by a membrane, contains instructions to make ribosomal RNA.

• Ribosomes: Consist of equal parts ribosomal RNA and proteins, closely connected with protein synthesis.

• Chromosome Complement: Describes number, size, and morphology of chromosomes in an individual or species.

• Karyotype: Describes chromosome complement in terms of number, size, and morphology.

• Nuclear Division: Chromatin fibers condense and form chromosomes during cell division, nucleolus disappears and reappears post-division.

• Trisomy and Monosomy: Conditions resulting in an abnormal number of chromosomes.

• Chromosome Numbers: Each species has a characteristic number of chromosomes.

• Ribosomal RNA Production: In the nucleolus, chromosomal DNA transcribes ribosomal RNA, which then associates with proteins to form ribosomal particles.

• Nuclear Envelope: Outer membrane continuous with rough endoplasmic reticulum, inner membrane anchored to nuclear lamina.

• Nuclear Lamina: Protein filament meshwork adjacent to inner membrane, provides support and shapes nuclear envelope, aids in positioning of nuclear pores.

• Nuclear Pore: Thousands present, octagonal structure with a ring-like arrangement called a pore complex, allows transport of water-soluble molecules across the nuclear envelope.

• Nucleoplasm: Highly viscous liquid in nucleus, contains nucleotides and enzymes, network of fibers called nuclear matrix present.

• Chromatin: Threads and fibers in nucleoplasm when cell not dividing, comes in two types: euchromatin (relatively dispersed, DNA transcribed) and heterochromatin (condensed, DNA not transcribed).

• Nucleosome: Basic unit of chromatin, DNA coiled around a protein unit called a histone.

• Chromatin Packing: Chromatin undergoes several levels of coiling to form a chromosome.

• Nuclear Matrix: Fiber network in nucleoplasm, similar to cell cytoskeleton.

• Chromosomes: Chromatin fibers condense and form chromosomes visible during cell division.

• Nucleolus: Dense basophilic material in nucleoplasm, not enclosed by a membrane, contains instructions to make ribosomal RNA.

• Ribosomes: Consist of equal parts ribosomal RNA and proteins, closely connected with protein synthesis.

• Chromosome Complement: Describes number, size, and morphology of chromosomes in an individual or species.

• Karyotype: Describes chromosome complement in terms of number, size, and morphology.

• Nuclear Division: Chromatin fibers condense and form chromosomes during cell division, nucleolus disappears and reappears post-division.

• Trisomy and Monosomy: Conditions resulting in an abnormal number of chromosomes.

• Chromosome Numbers: Each species has a characteristic number of chromosomes.

• Ribosomal RNA Production: In the nucleolus, chromosomal DNA transcribes ribosomal RNA, which then associates with proteins to form ribosomal particles.

Test your knowledge of cell ultrastructure with a focus on the nucleus, including the nuclear envelope, pores, karyoplasm, euchromatic and heterochromatic nuclei, and characteristic number of chromosomes. This quiz also covers the structure and function of the nucleolus.