Biology 1002B Lecture Notes - Lecture 15: Cytosine, Lac Repressor, Regulatory Sequence
15 Mar 2013
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Lecture 15: epigenetics: identical twins are not: histones, regulation of gene expression. Small +ve charged basic proteins attracted to ve charged phosphate in eukaryotic dna chromosomes: reasons why, if identical twin women have sons with identical twin men, the sons will not be identical. Dna from mom and dad is different. Doesn"t mean 50% chance of getting disease: characteristics that would, and would not, be different between monozygotic (identical) twins. Random x chromosome inactivation (females) by noncoding rna: process of random x inactivation leading to genetic mosaicism. Inactivate genes on either (maternal/mom or paternal/dad x: don"t need twice the product of those genes. Condensation process folds, packs chromatin of inactive x chromosome into dense chromatin (barr body) Inactivation occurs during embryonic development after divided into 100 cells. All descendants of the cell will be inactive as well. In humans, female skin cells are inactive or active but can"t tell because skin pigments aren"t on.
