Which one of the following statements is $NOT$ true regarding crossing over during meiosis?

Genetic maps of chromosomes are based on the frequency of $:-$

Genes $A$ and $B$ are linked. What will be the genotypes of the offspring produced from a cross between $AB/ab$ and $ab/ab$?

Mendel observed that some characters did not assort independently. Later researchers found it to be due to

How many linkage groups are present in bacteria?

$A$ 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 $B$. An offspring of this cross was crossed with a homozygous recessive for both the characters $A$ and $B$. The following results were 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: