Unformatted text preview: clumped. Highly condensed chromatin regions are called heterochromatin. Heterochromatin is too compacted to be transcribed. The less compacted regions of chromatin are known as euchromatin and can be transcribed. Inactive DNA contains nucleotides (especially cytosine) have methyl groups (-CH 3 ) attached. (The Barr body (see later) is an example of a chromosome that is highly methylated.) Most methylated DNA will remain inactive during differentiation and cell divisions. Methylation keeps some genes permanently turned off. Adding an acetyl group (-COCH 3 ) to the histone proteins associated with DNA helps transcription. Histones with acetyl groups bind more loosely to DNA ....
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.
- Spring '10