What is the correct sequence of the following events

$1.$Formation of the chromosome theory of heredity

$2.$Experiments which proved that $DNA$ is the hereditary material

$3.$Mendel's laws of inheritance-discovery

Code :

Match the following:

Choose correct answer :

$(i)$ Queen Elizabeth shows a number of haemophilic descendents.

$(ii)$ Variation in blood group prevalences due to incomplete dominance.

$(iii)$ Drosophila has three pairs of autosomal chromosomes.

$(iv)$ In birds, female is heterozygous.

Pick out the correct statements.

$(1)$ Haemophilia is a sex­linked recessive disease.

$(2)$ Down’s syndrome is due to aneuploidy.

$(3)$ Phenylketonuria is an autosomal recessive gene disorder.

$(4)$ Sickle cell anaemia is an $X$-­linked recessive gene disorder.

Which of the following pairs is $wrongly$ matched?