We don't know if this is the case. Looking at squib/wizard descent rates from wizard/muggle marriages would be an obvious additional test of Harry's genetic hypothesis, which he hasn't done. We don't know if Harry is correct about there being a single wizard gene.
I really don't get how the genetics works in either MOR or canon. In canon, there are wizards with one wizard parent and one muggle parent, who aren't squibs (Snape and Riddle for two). That implies it's dominant. Also, squibs in canon are born to 2 wizard parents (Neville's pure-blood and was thought to be one, and it's mentioned in the definition), and squibs are implied to be pretty uncommon, which they wouldn't be if they were all heterozygotes. In the end, though, I support EY's right to make it work out however he feels like, because canon is confused and self-contradictory and MOR's point about complex adaptations being either ubiquitous or absent is true.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 81, which should be published later today. The previous thread passed 400 comments as of the time of this writing, so it will pass 500 comments soon after the next chapter is posted, if not before. I suggest refraining from commenting here until chapter 81 is posted; comment in the 12th thread until you read chapter 81. After chapter 81 is posted, I suggest all discussion of previous guesses be kept here, with links to comments in the previous thread.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.) When posted, chapter 81 should appear here.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight,nine, ten, eleven, twelve.
As a reminder, it’s often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: