Who discovered epistasis?

In sweet peas,genes $C$ and $P$ are necessary for colour in flowers. The flowers are white in the absence of either or both the genes. What will be the percentage of coloured flowers in the offspring of the cross $Cc\ pp \times cc\ Pp$ (in $\%$)?

Extranuclear inheritance is observed in .......... .

In $Drosophila$,irregularities are observed during the differentiation of organs. For example,long appendages are formed in place of wings. Which gene is responsible for this?

In which type of inheritance is the result affected by reciprocal crosses?

Where are the cytoplasmic genes for male sterility typically located?