Which of the following is $NOT$ true for $Drosophila$ $melanogaster$?

In sickle cell anaemia$-$

The presence of four horns instead of two in a goat is an example of what?

Give differences: Incomplete dominance and Co-dominance.

Select the incorrect statement from the following.

In a plant,three dominant genes $A$,$B$,and $C$ must be expressed together to produce purple flowers. If any one or all three genes are in the recessive state,the flowers become colorless.
Raw material $\xrightarrow{A} X \xrightarrow{B} Y \xrightarrow{C} Z$ (Pigment)
$A$ purple-flowered plant with genotype $AABBCC$ is crossed with a colorless plant with genotype $aabbcc$. This results in $F_1$ hybrid purple offspring. What will be the proportion of purple-flowered plants in the $F_2$ generation produced by selfing the $F_1$ generation?