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

With the help of an example,differentiate between incomplete dominance and co-dominance.

$A$ gene which suppresses the activity of another gene but does not lie on the same locus is called:

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?

Assertion $A$: Gene is the unit of inheritance.
Reason $R$: The properties of tissues are due to the constituents of their cells.
Which option is correct for Assertion $A$ and Reason $R$?

In which plant was the lethal gene first observed?