1. The problem statement, all variables and given/known data According to genetic linkage theory, observed frequencies of four phenotypes resulting from crossing tomato plants are in the ratio 9/16 + a : 3/16 - a : 3/16 - a : 1/16 + a. In 1931, J.W. MacArthur reported the following frequencies: Observed Phenotype frequency Tall, cut-leaf 926 Tall, potato-leaf 288 Dwarf, cut-leaf 293 Dwarf, potato-leaf 104 Total 1611 Write down the likelihood of a given these observations. Find the maximum likeli- hood estimate of a, use it to calculate expected frequencies for the four phenotypes and compare them with the observed frequencies. Does genetic linkage theory look plausible? 2. Relevant equations likelihood of a data set (x1...xn) occuring is the product of fX(x), if Xi are independent. Then I could find max likelihood etc as usual 3. The attempt at a solution Basically I just cannot start this problem at all. I have only ever found likelihood before as a function producing one value, here I seem to want to find the probability that the ratio is b:c:d:e which I have no idea how to do. Also surely I need to know something about the variance of a? At least then I could write down a probability to do with each bit of the ratio? Sorry if I'm not making much sense/if this is obvious but I have spent a long time attempting this with no luck. Google hasn't helped at all either..