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Nuclear envelope• Nearly all of the cellular DNA in the nucleus in eukaryotic cell.• Bilayer :
– Inner membrane : contact with a meshwork of intermediate filament, the nuclear lamina
– Outer membrane : contiguous with the membrane of the endoplasmic reticulum (ER)
– Periplasmic space : between the inner and outer membranes• Components :
– DNA– RNA– Nuclear proteins (structural proteins, DNA and RNA polymerase, RNA-pro
cessing proteins, histones, and gene regulatory proteins) are synthesized in the cytoplasm on free ribosomes and are brought into the nuclear compartment.
• Nuclear pore : continues
Nuclear pore• Ions and small molecules (9nm diameter (<60kDa))
can pass through it. ==> prevent bulk exchage• 60kDa < nuclear protein ==> selective transport ac
ross the nuclear membrane, receptor mediated process
• Ex1, nucleoplasmin, 165-kDa, in frog oocyte nuclei– EM labeled with gold particle– COOH-terminal region (signal peptide)– ATP dependent
up which allows membrane lipid attachment• Lamin C• Gene, alternative splicing (A,C) and distinct gene (B)• The biochemical function of the nuclear matrix is uncl
ear. – heterogenous nuclear RNA(hnRNA) are enriched in nuclear matrix --> RNAs don’t diffuse within nucleoplasm and they are bound to nuclear matrix as they are spliced to be mature form
1-condensation of chromosome2-breakdown of nuclear envelope
Lamin kinase-->Lamin A,B,C phosphorylate-->depolymerisation of nuclear lamina
Lamin B remains associated with nuclear envelopeLamin A & C are dispersed within theprometaphase cell.
Genome• Nucleus contains almost all of the genetic informa
tion of the cell in the form of DNA.• The total genetic information stored within the chr
omosome --> genome• 3 functional domains
– Origin : point of initiation– Kinetochore : attachment for mitotic spindle– Telomere : maintenance of chromosomal structure, CG r
epeats enriched• Chromatin : DNA + Protein (histone+nonhistone pr
otein)
Right handed corner= sex chromosome
Chromosomal protein
• Histone protein – only in eukaryotic cell– The most abundant protein– rich (+) charge arginine & lysine, so can bind to (-) char