WHAT MIGHT A FAMILY'S PUZZLES LOOK LIKE?
Answers: Which puzzle piece is responsible for whirling disorder?
All individuals with whirling disorder (1, 3, 6, 8, 10, 11 and 12) must share a puzzle piece. Is there a color of puzzle piece that all affected individuals share?
Here's another way to think about it:
Since individual #1 on the pedigree both has the disorder and all red puzzle pieces, then you know that the puzzle piece responsible for the disorder must be red as well.
How do you know which piece it is? Search through the puzzles of those who have the disorder (1, 3, 6, 8, 10, 11 and 12) to find the puzzle with the fewest red pieces. Puzzles 6 and 12 have three red pieces; puzzles 5 and 11 have four.
Which of these pieces is shared by all three puzzles? Only piece #36!
Now check your work. Do any of the puzzles of the unaffected individuals (2, 4, 5, 7 and 9) have a red #36 puzzle piece?
NO! Each of these individuals has a #36 puzzle piece of a different color. Congratulations! You found the disorder gene!!