Presentation40 - PackagingDNAintochromosomes DNA

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Packaging DNA into chromosomes DNA Winding 2x around histone proteins forms  nucleosomes Nucleosome winding forms 30-nm chromatin. Chromatin is looped forming 300-nm fiber. Fibers are wound further into a metaphase  chromosome.
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Human female karyotype
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Human male karyotype
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Y X XX Dosage Compensation: Drosophila female male There are twice the number of X chromosomes in female cells than in male cells.  To  compensate, males double the transcription rate of their single X.
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Polytene chromosomes:  Drosophila Some nuclei contain chromosomes that have  undergone replication with no subsequent  sister strand separation, mitosis, or cell  division.  These are “polytene chromosomes.”   They are especially evident in the salivary  gland cells of Drosophila larvae.  The  chromosomes appear as relatively long,  banded, ribbons in interphase nuclei.  The 
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This note was uploaded on 02/26/2012 for the course AGRY 320 taught by Professor Stewert during the Spring '09 term at Purdue University-West Lafayette.

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Presentation40 - PackagingDNAintochromosomes DNA

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