p.2
Nuclear Envelope Composition
What is the main function of the nuclear envelope?
To enclose the nucleus and separate its contents from the cellular cytoplasm.
p.3
Structure and Function of the Nucleus
Are the contents of the nucleus uniform?
No, the interior of the nucleus contains subnuclear bodies made up of unique proteins, RNA molecules, and parts of chromosomes.
p.13
Nuclear Lamina and Mechanical Support
What provides mechanical support to the nucleus in animal cells?
Two networks of intermediate filaments, including the nuclear lamina.
p.13
Nuclear Lamina and Mechanical Support
Where is the nuclear lamina located?
On the internal face of the nuclear envelope.
p.11
Role of the Nucleolus in Ribosome Assembly
Is the nucleolus surrounded by a membrane?
No, it is not surrounded by a membrane.
p.8
Nuclear Pores and Transport Mechanisms
What extends into the nucleoplasm from the nuclear pore ring?
A structure called the nuclear basket.
p.16
Chromosomes and Genetic Material Organization
How are nuclear chromosomes packaged in eukaryotes?
By proteins into a condensed structure called chromatin.
p.3
Nuclear Pores and Transport Mechanisms
Why is nuclear transport crucial to cell function?
It is required for both gene expression and chromosomal maintenance.
p.12
Role of the Nucleolus in Ribosome Assembly
What is the first step in ribosomal assembly?
Transcription of rDNA by RNA polymerase I, forming a large pre-rRNA precursor.
p.14
Chromosomes and Genetic Material Organization
What happens to chromatin during cell division?
It forms well-defined chromosomes that can be seen in a karyotype.
p.7
Nuclear Pores and Transport Mechanisms
What is the molecular weight of nuclear pores?
About 125 million daltons.
p.17
Chromosome Structure and Duplication
What is a chromatid?
One of the two identical parts of a chromosome after the S phase.
p.2
Nuclear Lamina and Mechanical Support
What is the nuclear lamina and its role?
It provides mechanical support within the nucleus, similar to how the cytoskeleton supports the cell.
p.14
Chromosomes and Genetic Material Organization
What are chromosomes made of?
Multiple linear DNA molecules organized into structures.
p.1
Structure and Function of the Nucleus
What is the nucleus often referred to as in cell biology?
The 'control center' of the cell.
p.8
Nuclear Pores and Transport Mechanisms
What shape is the structure found at each nuclear pore?
Donut-shaped, eightfold-symmetric ring.
p.3
Nuclear Pores and Transport Mechanisms
How is the movement of larger molecules like proteins regulated?
It requires active transport regulated by carrier proteins.
p.10
Nuclear Pores and Transport Mechanisms
Where are nuclear pores located?
On the surface of the nuclear envelope.
p.8
Nuclear Pores and Transport Mechanisms
How many nuclear pores does a typical mammalian cell nucleus have?
About 3000 to 4000 pores.
p.13
Nuclear Lamina and Mechanical Support
What is the composition of the nuclear lamina?
Mostly composed of lamin proteins.
p.11
Role of the Nucleolus in Ribosome Assembly
What is the nucleolus?
A discrete densely stained structure found in the nucleus.
p.5
Nuclear Envelope Composition
What is the distance between the inner and outer membranes of the nuclear envelope?
10 to 50 nanometers (nm).
p.16
Chromosomes and Genetic Material Organization
What does a chromosome contain?
Many genes, regulatory elements, and other nucleotide sequences.
p.15
Types of Chromatin: Euchromatin and Heterochromatin
What are the two types of chromatin?
Euchromatin and heterochromatin.
p.1
Chromosomes and Genetic Material Organization
What are chromosomes made of?
Long linear DNA molecules complexed with proteins like histones.
p.14
Chromosomes and Genetic Material Organization
What does the cell nucleus contain?
The majority of the cell's genetic material in the form of chromosomes.
p.5
Nuclear Envelope Composition
What are the two membranes that make up the nuclear envelope?
An inner membrane and an outer membrane.
p.16
Chromosomes and Genetic Material Organization
What is a chromosome?
An organized structure of DNA and protein found in cells.
p.12
Role of the Nucleolus in Ribosome Assembly
What aids the processing and assembly of rRNA in the nucleolus?
Small nucleolar RNA (snoRNA) molecules.
p.11
Role of the Nucleolus in Ribosome Assembly
What are nucleolar organizer regions (NOR)?
Regions of DNA coding for ribosomal RNA (rRNA).
p.16
Chromosomes and Genetic Material Organization
What allows long DNA molecules to fit into the cell nucleus?
The packaging of chromosomes into chromatin.
p.17
Chromosome Structure and Duplication
What is the function of the centromere?
It is the point where the two chromatids touch and where the microtubules attach.
p.2
Nuclear Pores and Transport Mechanisms
Why are nuclear pores necessary?
Because the nuclear membrane is impermeable to most molecules, allowing movement across the envelope.
p.13
Nuclear Lamina and Mechanical Support
How are lamins synthesized?
They are synthesized in the cytoplasm and then transported into the nucleus.
p.3
Nuclear Pores and Transport Mechanisms
What do nuclear pores allow for?
Free movement of small molecules and ions.
p.10
Nuclear Pores and Transport Mechanisms
What are the components labeled in a cross section of a nuclear pore?
Outer ring, spokes, basket, and filaments.
p.14
Chromosomes and Genetic Material Organization
What is chromatin?
A DNA-protein complex that organizes chromosomes during most of the cell cycle.
p.7
Nuclear Pores and Transport Mechanisms
What are nuclear pores composed of?
Multiple proteins collectively referred to as nucleoporins.
p.5
Nuclear Envelope Composition
What is the function of the nuclear envelope?
To separate the cell's genetic material from the surrounding cytoplasm and prevent macromolecules from diffusing freely.
p.12
Role of the Nucleolus in Ribosome Assembly
What is significant about the assembled ribosomal subunits?
They are the largest structures passed through the nuclear pores.
p.1
Chromosomes and Genetic Material Organization
What is the nuclear genome?
The genes within the chromosomes of the nucleus.
p.11
Role of the Nucleolus in Ribosome Assembly
How does ribosomal assembly affect the nucleolus?
It results in the transient association of nucleolar components, facilitating further ribosomal assembly.
p.16
Chromosome Structure and Duplication
What characterizes unduplicated chromosomes?
They are single linear strands.
p.9
Nuclear Transport Proteins: Karyopherins
What type of molecules can diffuse through the cell membrane and bind to nuclear receptor proteins?
Steroid hormones and small lipid-soluble molecules.
p.1
Chromosomes and Genetic Material Organization
What does the nucleus contain that is crucial for genetic information?
Most of the cell's genetic material organized as DNA molecules.
p.13
Nuclear Lamina and Mechanical Support
What role does the nuclear lamina play in relation to chromosomes?
It provides anchoring sites for chromosomes.
p.5
Nuclear Envelope Composition
What is the relationship between the outer nuclear membrane and the rough endoplasmic reticulum?
The outer nuclear membrane is continuous with the membrane of the rough endoplasmic reticulum (RER).
p.15
Types of Chromatin: Euchromatin and Heterochromatin
What is heterochromatin?
The more compact DNA form that contains DNA that is infrequently transcribed.
p.1
Gene Expression Regulation by the Nucleus
What is one of the primary functions of the nucleus?
To maintain the integrity of genes and regulate gene expression.
p.9
Nuclear Transport Proteins: Karyopherins
How do most karyopherins interact with their cargo?
Directly, although some use adaptor proteins.
p.15
Types of Chromatin: Euchromatin and Heterochromatin
What are chromosome territories?
Discrete individual patches that chromatin organizes into during interphase.
p.12
Role of the Nucleolus in Ribosome Assembly
What are some sources of small nucleolar RNA (snoRNA)?
Derived from spliced introns from messenger RNAs encoding genes related to ribosomal function.
p.11
Role of the Nucleolus in Ribosome Assembly
What are the main roles of the nucleolus?
To synthesize rRNA and assemble ribosomes.
p.16
Chromosome Structure and Duplication
What are the two forms in which chromosomes may exist?
Duplicated or unduplicated.
p.15
Types of Chromatin: Euchromatin and Heterochromatin
What is constitutive heterochromatin?
Heterochromatin that consists of chromosome structural components such as telomeres and centromeres.
p.9
Gene Expression Regulation by the Nucleus
What role do nuclear receptor proteins serve when bound to their ligand?
They act as transcription factors.
p.7
Nuclear Pores and Transport Mechanisms
How many proteins do nuclear pores consist of in yeast and vertebrates?
Around 50 in yeast and 100 in vertebrates.
p.4
Role of the Nucleolus in Ribosome Assembly
What is the main function of the nucleolus?
Involved in the assembly of ribosomes.
p.13
Nuclear Lamina and Mechanical Support
What additional support does the nuclear envelope receive?
Less organized support on the cytosolic face of the envelope.
p.15
Types of Chromatin: Euchromatin and Heterochromatin
What is facultative heterochromatin?
Heterochromatin that consists of genes organized as such only in certain cell types or stages of development.
p.7
Nuclear Pores and Transport Mechanisms
What must happen for larger molecules, such as nucleic acids and larger proteins, to enter or exit the nucleus?
They must be actively transported.
p.15
Types of Chromatin: Euchromatin and Heterochromatin
What is euchromatin?
The less compact DNA form that contains genes frequently expressed by the cell.
p.8
Nuclear Pores and Transport Mechanisms
What types of molecules are transported through nuclear pore complexes?
Most proteins, ribosomal subunits, and some RNAs.
p.7
Nuclear Pores and Transport Mechanisms
What type of molecules can freely pass through nuclear pores?
Small water-soluble molecules.
p.16
Chromosome Structure and Duplication
What characterizes duplicated chromosomes?
They contain two copies joined by a centromere.
p.15
Types of Chromatin: Euchromatin and Heterochromatin
Where are active genes generally located in relation to chromosome territories?
Towards the chromosome's territory boundary, typically found in the euchromatic region.
p.8
Nuclear Pores and Transport Mechanisms
What is the role of the nuclear basket and filamentous extensions?
To mediate binding to nuclear transport proteins.
p.6
Role of the Nucleolus in Ribosome Assembly
What is the function of the nucleolus within the nucleus?
It is involved in ribosome assembly.
p.4
Structure and Function of the Nucleus
What is the average diameter of the nucleus in mammalian cells?
Approximately 6 micrometers (μm).
p.16
Chromosome Structure and Duplication
What results from the compaction of duplicated chromosomes during mitosis and meiosis?
The classic four-arm structure.
p.6
Nuclear Envelope Composition
How is nucleoplasm similar to cytoplasm?
It is similar in consistency and function, found inside the nucleus compared to outside.
p.4
Structure and Function of the Nucleus
How does the nucleus appear in terms of shape?
As a dense, roughly spherical organelle.
p.4
Role of the Nucleolus in Ribosome Assembly
Where are ribosomes exported after being produced?
To the cytoplasm, where they translate mRNA.
p.13
Nuclear Lamina and Mechanical Support
What happens to lamins after they are transported into the nucleus?
They are assembled before being incorporated into the existing network of nuclear lamina.
p.5
Nuclear Envelope Composition
How is the perinuclear space related to the rough endoplasmic reticulum?
It is continuous with the RER lumen.
p.4
Structure and Function of the Nucleus
How does nucleoplasm compare to cytosol?
It is similar in composition to the cytosol found outside the nucleus.
p.9
Gene Expression Regulation by the Nucleus
What happens to many nuclear receptors in the absence of ligand?
They function as histone deacetylases that repress gene expression.
