Upload
phebe-patrick
View
222
Download
0
Tags:
Embed Size (px)
Citation preview
Molecular Biology
Eukaryotic Genome Structure
The human genome:nuclear and mitochondrial
components
Genetic Material in the Living Cells
Composition of Chromosome
DNA
Histones(Major proteins)
Non-histone(Small amounts)
p
q
Karyotype
chromosomes
DNA Condensation: Why?
Histones
Nucleosomes: The Basic Units of DNA Condensation
Chromatin “beads-on-a-string” structure (10 nm Fiber)
Histone H1 Binds the Nucleosome to Form the Chromatosome
Two models of the 30 nm chromatin fiber
Two models of the 30 nm chromatin fiber
Higher-Order Chromosome Structure Involves Loops and Coils
Looped chromatin fibre folds
Chromatin fibre loops along the protein scaffold
Low power high power
Scaffold protein
DNA loops
The major structures in DNA compaction
The major structures in DNA compaction (contd.)
Regulation of chromatin structure
• Post-translational modifications of histones• Exchange of canonical histones with their
alternative sequence variants.• Chromatin remodeling via ATP-dependent
complexes • DNA methylation
Chromosomes
Metaphase chromosomes in Eukaryota:–the highest level of chromatin structure (the most condensed)
–observed only during cell division
After cell division:–metaphase chromosomes disappear–chromatin condensation is reduced–genomic DNA exists in the form of
heterochromatin and euchromatin
Different forms of chromatin show differential gene activity
euchromatin
heterochromatin