BIOL308 Lecture 9: Lecture 9
8 Apr 2016
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Document Summary
Euchromatin consists of transcriptionally active dna, susceptible to dnase digestion. Heterochromatin less susceptible to dnase digestion and transcriptionally inactive a) constitutive heterochromatin - highly condensed inactive chromatin; consists of repetitive dna, very few genes b) facultative heterochromatin - not active in particular tissue. Forms under specific circumstancesand/or certain tissues to silence gene expression: x-chromosome inactivation (barr body formation, imprinting. Centromere specific sequences; attachment point for sister chromatids and spindle fibers (constitutive heterochromatin) Chromatin elements (elements: particular nucleotide sequences, dna regions!) Locus control regions shared control regions (usually upstream from gene clusters) control chromatin condensation. Matrix and scaffold associated regions mostly at-rich dna which anchors to the nuclear matrix. Insulators regulatory domains in dna - define domains of gene expression. Centromeres = chromosome regions (= regions in chromosomal dna) which contain the site of attachment for microtubules kinetochore. In situ hybridization of metaphase chromosomes shows satellite dna at centromeres (repetitive sequences) kinetochore = centromere with proteins spindle fibres originating from centrioles.
