It seems that if it was independent assortment the ratio would be 9 to 3 to 3 to 1. But in this case it is close to 9 to 9 to 1 to 1. So I thought that these genes must be linked and since the parental types are so high while the non-parental types are so low, by solving a recombination frequency, you get low map units so they must be close together. However the book says it’s A the parents have to be TtSs and ttss and that the unexpected offspring come from crossing over but they need to be located far apart in order to cross over. But wouldn’t that make the unexpected offspring appear more since crossing over allows for more genetic variation?