Comparison of Kullback's information on nuclear pedigrees with differe
nt numbers of offsprings was performed in a case when a marker gene wa
s codominant and the recessive or dominant control with complete penet
rance was supposed for the localized gene. This comparison resulted in
some conclusions about optimization of the sample collection. These c
onclusions are found to be invariant with respect to the recombination
fraction value determined by the simple alternative hypothesis, to th
e population frequencies of the genes considered and, within certain l
imits, to the disequilibrium parameter values.