Nucleus Flashcards
How much space does the nucleus occupy in the cell?
10%
How many nuclear pore complexes does the nucleus have?
3000-4000
What is the matrix in the nucleus called?
Nucleoplasm
What is the nuclear material stored as in the nucleoplasm?
Chromatin
How much DNA is in a human cell?
2m
Why are chromosomes neutral ?
DNA charge is negative and histones are positive.
What is euchromatin?
Most common type of DNA found in cells
Active chromatin which is involved in transcribing RNA to produce proteins.
What is heterochromatin?
The genetically inactive DNA.
In a typical cell 10% of the genome is heterochromatin.
Where is heterochromatin more concentrated?
Centromeres and telomeres
How are genes in euchromatin silenced?
By moving them to the heterochromatin
What do nucleoli do?
Manufacture the subunits that make up ribosomes
What is the granular material in the nucleolus?
Ribsomal subunits that have already been formed
What is the space between the outer and inner membranes of the nuclear envelope called?
Perinuclear space
What signals are used to transport RNA and ribosomal subunits to the cytoplasm?
Nuclear export signals
What is a chromosome?
Single linear molecule of dna which contains genes
What do telomeres do?
Protect the end of the chromosome from degradation by forming G quadruplexes
How big are chromosome territories?
2 um
Where are euchromatin and heterochromatin found?
Euchromatin is in the interior of the nucleus and heterochromatin is in the periphery of the nucleus.
What 3 key features to scientists use to identify chromosomes?
βSIZE
βBANDING PATTERN
βCENTROMERE POSITION
List 6 nuclear compartments and their functions.
βCHROMOSOME TERRITORIES: they store DNA and control access to it
βREPLICATION FACTORIES: nascent DNA (lagging strand) production
βTRANSCRIPTION FACTORIES: nascent RNA (lagging strand) production
βSPLICEOSOME: irregular domains containing splicing factors
βNUCLEOLI: ribosome biogenesis
βPML NUCLEAR BODIES: possible nuclear depot.
What are 3 functions of the nucleolus?
β transcription of rRNA genes to produce a large 45S precursor
βcleavage/modification of rRNA into 18S, 5.8S and 28S rRNA
βassembly of ribosomal subunits (18S, 5.8S, 5S and 28S)
What are the 3 distinct zones of the Nucleolus:
βFibrillar Centre: Ribosomal RNA genes.
βDense Fibrillar Component: rRNA transcripts
βGranular Component: Processing and Assembly
What can move via Nuclear Pore Complexes:
βNuclear Export: ribosomal subunits and mRNA, Proteins require a nuclear export signal.
βNuclear Import: Histones, DNA/RNA polymerases and other nuclear proteins.β
How does the position of centromere differ:
βMetacentric = Centromere in centre. βSubmetacentric = Centromere close to centre. βAcrocentric = Centromere far away from centre.
What are the main Functions of the Nucleus:
βStores cells DNA. βDNA replication. βTranscription (making RNA). βRibosomal biogenesis. βControls communication between nucleoplasm and cytoplasm.
Outline the basic Chromosome structure:
βTelomeres: protect chromosome ends. βCentromeres (primary constriction): needed during cell division. βMultiple origins of replication. βQ arm longer βP arm shorter
How are Chromosomes identified in the lab:
βG banding: Chromosomes partially digested and stained with (giemsa).
βG dark: gene poor, heterochromatin rich.
βG light: gene rich, euchromatin rich.
βForms a unique banding pattern (like barcode).β
How is the Nucleus organised:
βFunctional Nuclear Compartmentalisation:
Subnuclear compartments exist despite the absence of internal membranes.β