Nucleus and Chromosomes Flashcards

Flashcards based on the lecture notes about Nucleus and Chromosomes.

What are the differences between eukaryotic and prokaryotic cells?

Membrane-bounded compartments, membrane-bounded nucleus, protein scaffolding (cytoskeleton), and compartmentalization.

What are the phases of interphase in the cell cycle?

G1, S, and G2 phases.

What are the main structures within the nucleus in interphase?

Nuclear envelope, nucleolus, chromatin & chromosome, and nuclear matrix.

What are the key objectives in understanding the eukaryotic cell nucleus?

To understand the components and function of the nuclear envelope, how eukaryotic cells fold long DNA molecules, Ribosome Biogenesis, and Nuclear Matrix.

What are the major components of the eukaryotic nucleus?

Nuclear envelope, chromosomes, nucleolus, and nuclear matrix.

What structures comprise the nuclear envelope?

Outer & inner membrane, continuity with ER, nuclear lamina, and nuclear pore complex.

What are the components of the nuclear envelope's complex structure?

Inner nuclear membrane, outer nuclear membrane, perinuclear space, and nuclear pore.

Approximately how many nuclear pore complexes (NPCs) are in a vertebrate cell's nuclear envelope?

Around 2000.

What is the main function of nuclear pores?

Facilitates material transport between the nucleus and cytoplasm.

What are the distinct components of the nuclear pore complex (NPC)?

Nuclear ring, cytoplasmic ring, central transporter, spokes, and basketlike fibers.

How do molecules traffic through the NPC?

Passive diffusion for small molecules and active transport with energy dependence for macromolecules.

What functions does the NPC serve in molecular transport?

Acts as a barrier, allows diffusion of small molecules, and controls passage of proteins & RNA complexes.

What is the function of the Nuclear Localization Sequence (NLS)?

Directs nuclear proteins to the nucleus for transport through the NPC.

Which proteins contain NLS for transport through the NPC?

Histones, DNA polymerases, RNA polymerases, transcription factors, and splicing factors.

What is the NLS sequence of the T antigen encoded by virus SV40?

pro-lys-lys-lys-Arg-lys-val

What components are involved in protein import through the NPC?

Importin α+β, nuclear pore complex, Ran-GTP, Ran-GDP, Ran-GAP, and Ran-GEF.

What are the key steps in protein import through the NPC?

Proteins with NLS bind to importin α, importin β binds to cytoplasmic filaments, the complex transports through the nuclear pore, Ran-GTP binds to importin β, and cargo protein is released.

What is the nuclear lamina?

A dense network made from fibrous protein called lamins.

What are the functions of the nuclear lamina?

Provides mechanical support and is a key element in nuclear envelope breakdown at mitosis.

How is the nuclear lamina regulated?

Regulated by phosphorylation and dephosphorylation.

What human diseases are associated with mutations in LMNA, a lamin gene?

A rare form of muscular dystrophy (EDMD2) and Hutchinson-Gilford progeria syndrome (HGPS).

What drug received FDA approval for treating progeria (HGPS)?

Zokinvy (Lonafarnib).

How do materials travel between the nucleus and cytoplasm through nuclear pores?

Small molecules (MW < 50 kDa) travel by passive diffusion, while most proteins and RNAs use active transport.

What is the nucleolus?

Largest structure present inside the nucleus; dark staining zone.

What are the structures within the nucleolus as seen in the electron microscope?

Fibrillar centers (FC), dense fibrillar component (DFC), and granular component (GC).

What do the different regions of the nucleolus represent?

Sites of progressive stages of rRNA transcription, procession, and ribosome assembly.

Where is the rDNA gene in the chromosome of eukaryotic cells?

On the short arms of chromosomes with satellites (13, 14, 15, 21, 22).

Which human chromosomes have short arms with satellites containing rRNA genes (rDNA)?

13, 14, 15, 21, 22.

Which rRNAs do NORs in human chromosomes code for?

18s, 28s, 5.8s rRNA.

What is the primary function of the nucleoli?

Sites of rRNA gene transcription and processing.

What is the nucleolus' role in rRNA production?

Synthesizing and processing rRNA.

What role does the nucleoli play in ribosome assembly?

The assembly sites of ribosomal subunits.

What four kinds of RNA do eukaryotic ribosomes contain?

5S, 5.8S, 18S, and 28S rRNA.

Where does pre-rRNA processing occur?

The nucleolus.

What components are involved in the function of the nucleolus in ribosome synthesis?

Ribosomal proteins, 5S rRNA, and pre-rRNA.

Which rRNAs are part of the large (60S) ribosomal subunit in eukaryotic cells?

28S rRNA, 5.8S rRNA, and 5S rRNA.

Which rRNA is part of the small (40S) ribosomal subunit in eukaryotic cells?

18S rRNA.

What is the nuclear matrix?

A proteinaceous scaffold-like network that permeates the cell nucleus.

What is the composition of nuclear matrix?

Composed of actin and other proteins.

What are the key functions associated with the nuclear envelope?

(1) Nuclear pore complex; (2) selective transport of proteins; (3) transport of RNA.

What aspects are important in considering nucleolus and ribosome biogenesis?

Organization of the nucleolus (FC, DFC, GC), rRNA genes and transcription (NOR), and ribosome biogenesis.

What is the function of the nuclear envelope regarding transport?

Selective transport of proteins to and from the nucleus, and transport of RNA between nucleus and cytoplasm.

What is the organization of the nucleolus?

Organization of the nucleolus (three distinct regions: FC, DFC, GC); rRNA genes and transcription (NOR); ribosome biogenesis of nucleolus.

What is another term for nuclear matrix?

Nuclear skeleton.

What are the three distinct regions in the organization of the nucleolus?

FC, DFC, GC

How do small molecules travel across the nuclear envelope?

Passive diffusion.

What does NOR stand for in the context of nucleolus organization?

rRNA genes and transcription.

What is the main function of nuclear pore complex?

Molecular traffic.

Which molecule binds to importin beta during protein import?

Ran-GTP.

Which provides mechanical support to the nuclear envelope?

Nuclear lamina.