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The C value paradox

The C value paradox. The C value: total amount of DNA in the genome We would expect that the more complex the organism, the more DNA is needed to “run it” Therefore, we would expect a linear relationship between genome size and organism complexity. This idea appears to make sense:

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The C value paradox

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  1. The C value paradox • The C value: • total amount of DNA in the genome • We would expect that the more complex the organism, the more DNA is needed to “run it” • Therefore, we would expect a linear relationship between genome size and organism complexity. • This idea appears to make sense: • the more complex the organism is, the more genetic information it needs (larger C value) • In smaller organisms (viruses, bacteria) there is no room for excess DNA (smaller C value)

  2. continued • At the lower range of complexity, this holds: • Bacteria have smaller genomes than eukaryotes, and viruses have smaller genomes than bacteria. • In larger organisms, relationship breaks down • Organisms have DNA apparently in excess of what is needed; repetitive sequences, “junk DNA” • This is the C value Paradox, that in the most complex organisms, there doesn’t appear to be the expected relationship between complexity and genome size.

  3. Homework on the C Value Paradox • What does this relationship look like? • How does genome size change with the complexity of the organism? • How do you graph “complexity”? • We will use actual physical size for complexity. • You agree humans are more complex than bacteria, and they more complex than viruses?

  4. Directions • You will be provided with a table of organisms. • These are your independent variables: organism size. • You will sort through the sites and references provided to determine the genome size for each organism. • The size ranges and the amount of base pairs vary by orders of magnitude: log graph • Directions for homework at http://www.clt.astate.edu/dgilmore/Genetics/Genetics%20homework/genomesize.htm

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