linkage and recombination

crossing over in-between linked genes

• roughly even numbers of the parental (lots more than half) and recombinant classes (much less than half)

the recombinant frequency for 2 linked genes can be calculated as follows

• RF = (recombinants/ total meiotic products) x100

RF is roughly proportional to…

• the distance between the 2 loci

• the closer 2 genes are, the less likely there will be a recombination event in between them. So, the strength of linkage depends on the distance between the genes

recombinant frequency is always between…

• 0% and 50%

2 loci right next to each other

• no crossing over → no recombinants → 0% RF

2 loci on separate chromosomes

• 50% recombinant and 50% parental → 50% RF

2 loci on the same chromosome but far apart

• you will get more than 1 crossover in-between them

once the distance gets big enough…

• its impossible to differentiate between 2 genes very far apart on the same chromosome or 2 genes on separate chromosomes