Biology, 6th Edition

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Greg Steinberg AP Biology Chapter 19 The Organization and Control of Eukaryotic Genomes A. Eukaryotic Chromatin Structure a. DNA Packaging i. DNA has particular folding and packaging patterns. ii. DNA is packaged with many proteins that help pack the most DNA in the smallest amount of space. b. Nucleosomes i. Histones are proteins that help package DNA on the first level of DNA packaging. ii. There is the same amount of histones as there is DNA. iii. Histones are charged positive, DNA is charged negative, this is how they bind. iv. There are 5 different types of Histones. They are similar among eukaryotes. v. Histone genes have been conserved during evolution. vi. The chromatin is raveled around the histone; this bead is known as a nucleosome. vii. The bead remains intact throughout the cell cycle. c. Higher Level DNA packaging i. Chromosomes are even more condensed DNA. ii. The nucleosomes then form the 20-nm chromatin fiber with the aid of histone H1 protein. iii. This chromatin fiber is then bound by loops to a scaffolding protein. iv. The scaffolding protein then loops itself into a chromosome. v. Heterochromatin is the type of chromatin you can see in a light microscope, while euchromatin is not visible. B. Genome Organization at the DNA level a. Genetic Small Talk i. 97% of human DNA does not code for protein. ii.
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bio19 - Greg Steinberg AP Biology Chapter 19 The...

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