Who gave first experimental evidence of the polygenic concept of inheritance

$A $: Non-allosomic genic determination of sex is found in bacteria.
$R$ : Sex is dependent on some environmental factors in prokaryotes.

Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino

Self sterility in "Nicotiana'' was reported by

Which one of the following is not a mutagen