Which one of the following pair is correctly matched
Van Helmont$⇒$Discovered mutations
Louis Pasteur$⇒$Wrote "The Origin of Species''
T.H. Morgan$⇒$Studied sex-linked inheritance
H. Khorana$⇒$Studied $DNA$ replication
In a test cross involving $F_1$ dihybrid flies, more parentaltype offspring were produced than the recombinanttype offspring. This indicates
Frequency of crossing over in a chromosome is an index of
Morgan hybridised yellow-bodied, white-eyed females to brown-bodied, red-eyed males and intercrossed their $F_{1}$ progeny. He observed that
$(a)$ $F_{2}$ ratio was deviated very significantly from the $9 : 3 : 3 : 1$ ratio
$(b)$ Both genes did not segregate independently of each other
$(c)$ Recombinant types are not obtained in $F_{2}$ generation
$(d)$ Both genes segregate independently of each other
Select the correct set of statements :
Crossing over is