Chapter 12 - DNA Organization in Chromosomes

Chapter 12 - DNA Organization in Chromosomes - -polytene...

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Chapter 12 DNA Organization in Chromosomes viral and bacterial chromosomes are relatively simple DNA molecules - DNA in bacterial chromosomes is found to be associated with several types of DNA-binding proteins o HU and H small, abundant in cell, contain high percentage of positively charged amino acids that can bond ionically to the negative charges of the phosphate groups in DNA similar to histones associated with eukaryotic DNA supercoiling is common in the DNA of viral and bacterial chromosomes - supercoiled DNA particularly characteristic of closed circular molecules o least compact, least dense – demonstrated decrease in sedimentation velocity o more compact, more dense – greater velocities - topoisomers identical molecules that differ only in their linking number o topoisomerase catalytic molecules (type I or type II), cleaves strands specialized chromosomes reveal variations in structure
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Unformatted text preview: -polytene chromosomes found in various tissues in the larvae of some flies, as well as in several species of protozoans and plants o can be seen in the nuclei of interphase cells o linear series of alternating bands and interbands chromomeres individual bands puff uncoiling event-lampbrush chromosomes appearance is similar to brushes used to clean kerosene lamp chimneys in the nineteenth century o characteristic of most vertebrate oocytes and spermatocytes of some insects meiotic chromosomes DNA is organized in chromatin in eukaryotes-chromatin structure and nucleosomes o chromatin nucleoprotein structure that is composed of tightly coiled DNA and proteins o histones positively charged proteins o nonhistones less positively charged proteins...
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This note was uploaded on 04/17/2008 for the course BIOL 2500 taught by Professor Finger during the Fall '07 term at Rensselaer Polytechnic Institute.

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