Who traced a specific nuclear structure all through spermatogenesis in a few insects and named it $x-$body?

In $Drosophila$,sex determination is controlled by:

How is sex determined in various organisms? Give the historical background of sex determination.

$A$ family has $9$ daughters. What is the probability of having a son at the $10$th birth (in $\%$)?

$A$: One drumstick per nucleus is present in the neutrophil of a normal female.
$R$: It is absent in the neutrophil of a male.

$A$ man affected by a certain disease marries a normal woman. They have $8$ children ($3$ daughters and $5$ sons). All the daughters suffer from their father's disease,but none of the sons are affected. What type of inheritance can you suggest for this disease?