The ratio of genotypes can be determined by examining the Punnett square.
Let's find what each pair stands for in terms of ratios:
aa = 1/4
bb = 1/4
cc = 1/4
dd=1/4
Aa = 1/2
Bb = 1/2
hence,Â
1. aabbccdd = 1/4 x 1/4 x 1/4 x 1/4
           =  1/256
2. AaBbCcDd = 1/2 x 1/2 x 1/2 x 1/2Â
            =  1/16
3. AABBCCDD = 1/4 x 1/4 x 1/4 x 1/4Â
             = 1/2564.
4. AaBBccDd = 1/2 x 1/4 x 1/4 x 1/2Â
            = 1/64