In: Biology
What does it mean when two loci are
(a) unlinked
(b) partially linked
(c) completely linked?
Explain with respect to the expected phenotypic ratios in the F2 in a typical Mendelian dihybrid testcross (e.g. Assume two loci, A and B, with two alleles each, such that the A and B alleles are completely dominant over a and b).
When the genes are unlinked, they show independent assortment. They segregate independently of each other during gamete formation. All the gametes formed in this case are in equal ratio. In this case both parental and Recombinant gametes are formed.
When the genes are partially linked, then they do not show independent assortment. They do not segregate independently of each other during gamete formation. In this case both Recombinant and parental gametes are formed. All the gametes formed in this case are according to the distance present between the participating genes.
When the genes are completely linked with each other, then also they do not show independent assortment. In this case only parental gametes are formed in equal proportion.