BIOL 200 Lecture Notes - Lecture 42: Giemsa Stain, Sister Chromatids, Polytene Chromosome
22 Jun 2016
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Document Summary
Dnase and bamhi-digested dna subjected to southern blot analysis with probe of labeled cloned adult globin dna, which hybridizes to 4. 6-kb bamhi fragment. If globin gene is susceptible to initial dnase digestion, it would be cleaved repeatedly & would not show this fragment, thus the transcriptionally active dna does not have 4. 6-kb band on southern blot. Inactive dna from msb cells was resistant to digestion, thus inactive dna is in a more condensed form of chromatin that shields globin genes from dnase digestion (unacetylated histone lysine tails) 30-nm chromatin fiber of packed nucleosomes beads-on-a-string form of chromatin short interphase: extended scaffold-associated chromatin region of dna double helix. Heterochromatin: dark regions, contains more condensed material. Condensation of metaphase chromosomes results from several orders of folding of 30-nm chromatin fibers. Chromosomes that become visible during metaphase are duplicated structures; each metaphase chromosome consists of 2 sister chromatids, which are linked at centromere (constricted region) telomeres: end of chromatid.
