BIOL 200 Lecture 19: November 6
7 Jun 2016
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Document Summary
Metaphase vs. interphase: metaphase: highly condensed for transmission to daughter cells, interphase: this is the real functional chromosome, undergoing replication and transcription. Evidence for loops in interphase chromosomes: localization of specific genes by in situ hybridization. Each loop is a functional chromatin domain in terms of chromatin condensation and enhancer action. Scaffold-assocaited region (sar) or matrix-attachment region (mar) thought to function as an insulator or barrier to spreading chromatin condensation and to the action of enhancers. Chromatin loops visable in lampbrush chromosomes of an amphibian (newt) oocyt. Lampbrush chromosomes are highly transcriptionally active over long periods of time to build up the huge amounts of rna and proteins present in the mature oocyte a giant cell (~1 mm diameter) Because the cell, and its nucleus, is so large, the chromosomes spread out much more than is the case in cells of typical dimensions. Other type of giant interphase chromosomes are the polytene chromosomes of the fly (drosophila) salivary gland.
