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)

continued In larger organisms, relationship breaks down 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.

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?

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