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

Which of the following statements are incorrect? $(i)$ $ABO$ blood grouping is controlled by gene $I$. (ii) Gene $I$ has four alleles. (iii) $I^A$ and $I^B$ produce the same type of sugar. (iv) $I$ or $i$ produces a different type of sugar. $(v)$ $I^A$ and $I^B$ are incompletely dominant.

Which of the following pairs is $wrongly$ matched?

$A$ back-cross is a cross between ........

Which of the following are the main categories of genetic disorders?

When a plant of $F_1$ generation is crossed with homozygous dominant parents,it is known as