How do i calculate map units, percent of recombination, and find out if two genes are linked?

I have two genetic problems that i have no idea how to do. They give me the results of a cross of drosophila and ask:Would you say that these two genes are linked? If so, how many units apart are they on the chromosome.


Another question says: Give the percentage of recombination and the map distance between the genes.





I would like to know HOW to answer the questions. What are the formulas??

How do i calculate map units, percent of recombination, and find out if two genes are linked?
How many times did cross over (during meiosis) occur between the two genes in question to get the data that you have. If there was no recombination between the genes then the answer is zero. The two genes are always found together in the next generation. If the two genes were unlinked, i e on different chromosomes (or very far away on the same chromosome) then 50% of the time the different chomosomes would go to different cell during meiosis and 50% of the time they go to the same cell. Linkage is a statistical concept. Rf is between 0 and 50%. If Rf is 50% you cannot tell he difference between physicall linkage at a very long distance or two genes on different chromosomes. Your text book should have the formulas. Map units is based on observed recombination with a correction factor for double recombinants. Reread your text for the formulas