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A pure breeding pea plant with the dominant phenotype of character $A$ and recessive phenotype of character $B$ was crossed with another pure breeding plant with the recessive phenotype of $A$ and dominant phenotype of character $B. A$ offspring of this cross was crossed with a homozygous recessive for both the characters -$A$ and $B$. The following results are obtained $22$ were phenotypically dominant for $A$ and recessive for $B$.
$4$ were phenotypically dominant for both $A$ and $B$.
$4$ were phenotypically recessive for both $A$ and $B$.
$24$ were phenotypically recessive for $A$ and dominant for $B$.
These results show that
Genes $A$ and $B$ are linked
Independent segregation of genes $A$ and $B$
Mendelian dihybrid inheritance
Polygenic inheritance
Solution
(a) In this type of parents have the genotypes $AAbb$ and $aaBB$, when they are crossed the offsprings with the genotype $AaBb$ produced.
This offspring is crossed with the individual having the genotype aabb.
If the genes $A$ and $B$ show independent assortment, then the four types of offspring will be produced in the ratio $1 : 1 : 1 : 1$.
But this does not happen,
hence the genes $A$ and $B$ are linked.
