When an $F_1$ individual is crossed with either of the two parents,it is known as:

Select the group of $CORRECT$ statements.
$I$. If phenotype of offsprings shows only the dominant trait then the parent plants are heterozygous.
$II$. $A$ true breeding line shows stable trait inheritance and expression for several generations.
$III$. In mendelian experiment material,contrasting characters can be easily recognized.
$IV$. When a single gene controls two (or more) different traits,it is called polygene.
$V$. When interactions occurs between the alleles of different genes present on the same or different chromosome it is called intragenic interaction.

Explain the following terms with examples:
$(a)$ Co-dominance
$(b)$ Incomplete dominance

The $F_2$ dihybrid ratio $9 : 3 : 4$ is explained on the basis of

In a dihybrid cross,when one pair of alleles shows incomplete dominance,the resulting genotypic ratio will be ....

In a complementary gene interaction,calculate the number of phenotypes and genotypes produced in a cross $AaBb \times aaBB$.