Question

Why the proportion of parental gene combinations were much higher than the non-parental type.?

Answer 1

When the genes are linked, the proportion of parental gene combinations are much higher than non-parental types. When the genes for certain features (like black eyes​ and short wings of Drosophila) are located very close to each other on a chromosome, there are little chances of crossing over, giving higher parental combination. When the genes are on different locii on a chromosome, the distance between them being considerable, there are higher chances of recombination, giving rise to mixed or non parental features.