Select the correct statement from the ones given below with respect to dihybrid cross :

Q.

In a test cross involving $F_1$ dihybrid flies, more parental type offspring were produced than recombinant type offspring, this indicates

Q. Cystic fibrosis is caused due to

Q. A scientist performed the gene mapping experiments in maize. He mapped the genes on chromosomes on the basis of % crossing over between different genes. One map unit corresponds to one % crossing over or recombination. The genes showing more than 50% recombination were not supposed to be linked on same chromosome. In crossing over studies on maize, scientist observed the following % crossing over between genes A, B, C, D: between A and D 10%, between A and C 3%, between genes C and D 7%, between genes A and B 5%, and between genes C and B 8%. On the basis of above observation, find out the correct sequence of genes A, B, C and D on chromosomes.

Q. The percentage of crossing over between two linked genes determine their relative on a chromosome.

Q. Two linked genes a and b show $20\%$ recombination. The individuals of a dihybrid cross between $+$ $+/+$ $+$ $\times$ ab/ab shall show gametes.