GeneRegulation160-page6 - clumped Highly condensed...

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Gene Regulation - 6 Regulating Gene Expression in Eukaryotic Organisms Gene expression starts with transcription and “ends” with an enzyme catalyzing a particular chemical reaction, or with a structural/metabolic protein. Gene expression can be controlled at any level of gene activity. Making the DNA readable (or not) Transcription Activating transcription Frequency and rate of transcription Processing the mRNA Selective intron removal Translation Stability of mRNA can be blocked in the cytoplasm mRNA access to translation Post-translation Protein Modification Duration of gene product in the organism Enzyme Activity and Feedback Inhibition DNA Controls – Pre-transcription Chemical Modification of DNA During Interphase, many regions of a chromosome remain tightly condensed and
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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.

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