Variation refers to .......

Read the following statements carefully:
$(1)$ Ploidy is a structural chromosomal abnormality.
$(2)$ Hemophilia is an autosomal recessive disorder in which blood does not clot.
$(3)$ Recombination is one of the factors responsible for evolution.
$(4)$ Genetic mapping allows the determination of the specific location of a gene on a chromosome.
$(5)$ Snapdragon plant is an example of incomplete dominance.
$(6)$ $ABO$ blood grouping shows both dominance and codominance.
Identify the correct and incorrect statements from the given options.

Choose the correct option for the given descriptions:
$(i)$ The heterozygous female transmits the disease to the son.
$(ii)$ Change in the shape of the $RBC$ from biconcave disc to elongated sickle-like structure.
$(iii)$ Mentally retarded.
$(iv)$ Haemoglobin is not formed in the proper amount in the blood.

The science which links heredity with environments is known as:

Which of the following is $NOT$ true for $Drosophila$ $melanogaster$?

Differentiate between a monohybrid cross and a dihybrid cross.