You actually got closer to 533 because you included more characters than I did. Then someone corrected you with additional characters, so I suppose it will be upwards of 600.
Genetics fiction, or fiction that I feel references genetics:
Dr. Franklin's Island by Ann Halam
Chromosome 8 (see above)
The Tommyknockers by S. King
Animorphs by Applegate
Titan by John Varley
When the Wind Blows but you've already read it.
Dusk by Susan Gates
I know as a fact that there are others, but I left my library at home. It's difficult, because I don't consider something to be Genetics-based unless it involved serious physical alteration (Which is why I haven't picked up The Uglies series or Oryx and Crake) or severe mental alteration. I don't consider "athlete" or "piano prodigy" to be interesting genetics.