STRUCTURE AND
FUNCTION OF CELL
NUCLEUS, CHROMATIN
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SIGNIFICANCE OF STRUCTURE AND
FUNCTION OF CELL NUCLEUS IN MEDICINE
Example:
• Structure of nucleus: 21st chromosome
• Disease: Down syndrome
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STRUCTURE AND FUNCTION OF CELL
NUCLEUS, CHROMATIN:
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Structure of cell nucleus
Function of nuclear envelope
Function of nuclear lamina
Structure and function of chromatin
Function of nucleolus
Basic structure of chromosome
Structure of nucleosome
Structural levels of eucaryotic chromosome
Structure of mitotic chromosome
Regulation of chromatin structure
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1. STRUCTURE OF CELL NUCLEUS:
Nucleus contains most of the DNA of eucaryotic cell.
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Nuclear envelope
Nuclear lamina
Chromatin
Nucleolus
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2. FUNCTION OF NUCLEAR ENVELOPE:
Nuclear envelope: inner and outer membrane
nuclear pores [FIG.] [FIG.]
Nucleus is the place for DNA replicaton and DNA transcription which is
separated from translation in cytoplasm.
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2. FUNCTION OF NUCLEAR ENVELOPE:
Nuclear envelope: inner and outer membrane
nuclear pores [FIG.] [FIG.]
Nucleus is the place for DNA replicaton and DNA transcription which is
separated from translation in cytoplasm.
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3. FUNCTION OF NUCLEAR LAMINA:
Nuclear lamina: lamins [FIG.]
Mechanical support of nuclear envelope
Desintegration and reintegration of nuclear envelope in mitosis:
phosphorylation and dephosphorylation of lamins
[FIG.]
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3. FUNCTION OF NUCLEAR LAMINA:
Nuclear lamina: lamins [FIG.]
Mechanical support of nuclear envelope
Desintegration and reintegration of nuclear envelope in mitosis:
phosphorylation and dephosphorylation of lamins
[FIG.]
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4. STRUCTURE AND FUNCTION OF
CHROMATIN:
Chromatin: DNA & proteins (histones + nonhistone chromosomal
proteins) form linear chromosomes
• Heterochromatin
• Euchromatin
[FIG.] [FIG.]
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5. FUNCTION OF NUCLEOLUS:
Nucleolus: DNA coding for rRNA
Production of ribosomes
[FIG.] [FIG.]
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6. BASIC STRUCTURE OF CHROMOSOME:
Chromosome: DNA
histones (H1, H2A, H2B, H3, H4)
nonhistone chromosomal proteins
Histones: basic structure of chromosome (nucleosomes)
Nonhistone chromosomal proteins: three-dimensional arrangement of
chromosome
Nucleosome: bacis structural units of eucaryotic chromosome
Eukaryotic chromosome: linear, approximately 108 base pairs
Prokaryotic chromosome: circular, approximately 106-107 base pairs
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7. STRUCTURE OF NUCLEOSOME
Nucleosome: core made of histone octamer (2x H2A, 2x H2B, 2x H3,
2x H4)
DNA wound around the core (147 base pairs)
[FIG.]
Free DNA between nucleosomes (about 60 base pairs)
There are about 200 base pairs per one nucleosome.
Individual nucleosomes are joined by H1.
[FIG.]
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7. STRUCTURE OF NUCLEOSOME
Nucleosome: core made of histone octamer (2x H2A, 2x H2B, 2x H3,
2x H4)
DNA wound around the core (147 base pairs)
[FIG.]
Free DNA between nucleosomes (about 60 base pairs)
There are about 200 base pairs per one nucleosome.
Individual nucleosomes are joined by H1.
[FIG.]
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8. STRUCTURAL LEVELS OF EUCARYOTIC
CHROMOSOME:
Structural levels:
• double helix of DNA (the diameter of fiber is 2nm)
• nucleosomes with wound DNA (11nm)
• 30-nm chromatin fiber (30 nm)
• chromatin loops (decondensed chromosome) (300 nm)
• condensed part of chromosome (chromatid) (700 nm)
• entire mitotic chromosome (1400 nm)
[FIG.] [FIG.]
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9. STRUCTURE OF MITOTIC CHROMOSOME:
Mitotic chromosome: 2 chromatids
centromere
telomeres
Human chromosomes
[FIG.]
[FIG.] [FIG.]
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9. STRUCTURE OF MITOTIC CHROMOSOME:
Mitotic chromosome: 2 chromatids
centromere
telomeres
Human chromosomes
[FIG.]
[FIG.] [FIG.]
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10. REGULATION OF CHROMATIN STRUCTURE:
Chromatin remodeling complexes
[FIG.]
Histone modifications: acetylation, methylation, phosphorylation [FIG.]
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10. REGULATION OF CHROMATIN STRUCTURE:
Chromatin remodeling complexes
[FIG.]
Histone modifications: acetylation, methylation, phosphorylation [FIG.]
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LITERATURE:
• Alberts B. Et al.: Essential Cell Biology. Garland Science. New York
and London, pp. 179-193, 2010.
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