The Nucleus
- Created by: Amber Manley
- Created on: 08-01-14 19:38
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- The Nucleus
- What?
- Double membrane
- Supported by fibrous protein mesh
- Aquesous solution containing DNA, RNA and Proteins
- Why?
- Separate fragile chromosomes from cytoskeletal cytoplasmic filaments
- Separate Transcription from Translation
- RNA processing
- Regulation of RNA export
- Regulate export/import of other proteins
- DNA
- Phosphodiester bond
- Nucleotides linked by a covalent bond between 5' phosphate and 3' OH
- Sugar-Phosphate backbone of DNA
- Double Helix
- Store of genetic information
- Replication
- 2 strands separate, both forming templates
- Semi-conservative; each new strand of DNA has one original strand
- Replication
- Gene Expression
- Regulatory sequences say where transcription starts
- DNA strands separate (Transcription bubble)
- One strand acts as a template for RNA synthesis
- Phosphodiester bond
- Chromosomes
- Structure
- Centromeres
- attaches to mitotic spindle
- repetitive sequences
- Heavily Packaged
- Hold metaphase chromosomes together
- Telomeres
- Protective end of chromosome
- Special replication mechanism
- Shorten with age
- Centromeres
- Nucleosomes
- core nucleosomes made up of histone proteins
- 2 of each 4 proteins make up the histone octomer (H2A,H2B, H3, H4)
- Hydrogen bonds form between DNA and histone octomer
- Beads on a string - arrangement of condensed chromatin
- core nucleosomes made up of histone proteins
- thread to fibre
- H1 histone binds to nucleosome
- interactions between the 4 core histones help
- 10x packaging factor
- Looped Domains
- Structural proteins cause more packaging
- Further Condensing
- condensin proteins use ATP to further wind chromatin
- 10000x packaging factor
- Structure
- Nuclear Import
- Import receptors bind to nuclear localisation signal on cargo
- Complex then binds to proteins on the cytoplasmic filaments of the nuclear pore complex
- Sequentially binds to proteins further and further towards the nuclear side of the pore complex
- GTP causes a change in importin, complex breaks
- importin/GTP complex returns to cytoplasm
- GTP hydrolysed to GDP (transported back to the nucleus)
- importin released to continue cycle again
- Nuclear Lamina
- Fibrous meshwork that provides support for the nucleus
- extends in a loose meshwork
- Comprised of fibrous proteins called lamins
- Like other intermediate filaments, lamins associate with each other to form a higher order structure
- lipid like structures on the lamina bind it to the inner nuclear membrane
- Like other intermediate filaments, lamins associate with each other to form a higher order structure
- binds to chromatin through histones H2A and H2B
- Fibrous meshwork that provides support for the nucleus
- What?
- 3x packaging factor
- Nucleosomes
- core nucleosomes made up of histone proteins
- 2 of each 4 proteins make up the histone octomer (H2A,H2B, H3, H4)
- Hydrogen bonds form between DNA and histone octomer
- Beads on a string - arrangement of condensed chromatin
- core nucleosomes made up of histone proteins
- Nucleosomes
- Nuclear Envelope
- The Nucleus
- What?
- Double membrane
- Supported by fibrous protein mesh
- Aquesous solution containing DNA, RNA and Proteins
- Why?
- Separate fragile chromosomes from cytoskeletal cytoplasmic filaments
- Separate Transcription from Translation
- RNA processing
- Regulation of RNA export
- Regulate export/import of other proteins
- DNA
- Phosphodiester bond
- Nucleotides linked by a covalent bond between 5' phosphate and 3' OH
- Sugar-Phosphate backbone of DNA
- Double Helix
- Store of genetic information
- Replication
- 2 strands separate, both forming templates
- Semi-conservative; each new strand of DNA has one original strand
- Replication
- Gene Expression
- Regulatory sequences say where transcription starts
- DNA strands separate (Transcription bubble)
- One strand acts as a template for RNA synthesis
- Phosphodiester bond
- Chromosomes
- Structure
- Centromeres
- attaches to mitotic spindle
- repetitive sequences
- Heavily Packaged
- Hold metaphase chromosomes together
- Telomeres
- Protective end of chromosome
- Special replication mechanism
- Shorten with age
- Centromeres
- thread to fibre
- H1 histone binds to nucleosome
- interactions between the 4 core histones help
- 10x packaging factor
- Looped Domains
- Structural proteins cause more packaging
- Further Condensing
- condensin proteins use ATP to further wind chromatin
- 10000x packaging factor
- Structure
- Nuclear Import
- Import receptors bind to nuclear localisation signal on cargo
- Complex then binds to proteins on the cytoplasmic filaments of the nuclear pore complex
- Sequentially binds to proteins further and further towards the nuclear side of the pore complex
- GTP causes a change in importin, complex breaks
- importin/GTP complex returns to cytoplasm
- GTP hydrolysed to GDP (transported back to the nucleus)
- importin released to continue cycle again
- Nuclear Lamina
- Fibrous meshwork that provides support for the nucleus
- extends in a loose meshwork
- Comprised of fibrous proteins called lamins
- Like other intermediate filaments, lamins associate with each other to form a higher order structure
- lipid like structures on the lamina bind it to the inner nuclear membrane
- Like other intermediate filaments, lamins associate with each other to form a higher order structure
- binds to chromatin through histones H2A and H2B
- Fibrous meshwork that provides support for the nucleus
- What?
- 2 concentric membranes
- contigous but functionally distinct
- inner membrane attaches to nuclear lamina and chromatin
- outer membrane continuous with endoplasmic reticulum
- Nuclear Pore Complex
- Regulate flow of molecules in and out of the nucleus
- RNA molecules and ribosome subunits out
- Nuclear proteins and ribosome subunit in
- small molecules diffuse
- Large molecules are actively transported
- Regulate flow of molecules in and out of the nucleus
- The Nucleus
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