Artificially Intelligent

Any mimicry distinguishable from the original is insufficiently advanced.

Facts from ECB CH5: DNA and Chromosomes

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The Structure of Eukaryotic Chromosomes

  • human cells contain 2 meters of DNA
  • the human cell nucleus is only 5–8 μm in diameter
  • packaging of DNA is accomplished with specialized proteins that bind and fold. This generates a series of coils and loops that provide high levels of organization
  • bacteria have genes in a circular DNA molecule
  • The full set of human chromosomes contain 3.2 x 10^9 base pairs
  • chromosomes can be identified with dyes that bind to A-T pairs versus G-C pairs, which produce predictable bands.

The Regulation of Chromosome Structure

  • cells can alter chromatin structure to expose localized regions of DNA, which allows access to specific proteins.

  • ATP-dependent chromatic-remodeling complexes use ATP hydrolysis to change the position of DNA wrapped around nucleosomes
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  • Histones, which control how DNA is wrapped, can also be modified by enzymes
  • Most cells only express about half the genes they contain
  • Having two expressive X-chromosomes is lethal, so early in embryonic development one of them gets condensed into heterochromatin. Different X chromosomes sometimes have different expressions, e.g. in calico cats
  • When a cell divides, it can pass on histone modifications, chromatin structure, etc. This “cell memory” is critical for the establishment and maintenance of different cell types