Frequency of crossing over in a chromosome is an index of

Which of the following statements is not trueof two genes that show $50\%$ recombination frequency ?

There are three genes $a,\,b,\,c$. Percentage of crossing over between $a$ and $b$ is $20\%$, $b$ and $c$ is $28\%$ and $a$ and $c$ is $8\%$. What is the sequence of genes on chromosome ?

In a certain plant, red flowers $(R)$ are dominant to white flowers $(r)$ and tallness $(T)$ is dominant to dwarfness $(t)$. A heterozygous plant $(RrTt)$ is backcrossed with a double recessive plant $(rrtt)$. If the gene loci for colour and size and situated very close together on the same chromosome, the expected percentage of offsprings could be approximately

 respectively

When two genes are situated very close to each other in a chromosome

Give differences : Crossing over and Linkage