When the genes are completely linked the F2 dihybrid test cross ratio is:

When the genes are completely linked then crossing cover cannot take place. Therefore, no recombinant will be formed. Let’s understand this with an exampleP: AABB X aabbF1: AaBbTest cross: AaBb x aabbGametes for AaBb are AB and ab.Gametes for aabb: abHence the genotypes of offspring would be AaBb and aabb and the ratio is 1 : 1