$A$ back-cross is a cross between ........

Hybrids are generally more vigorous than their parents. This is due to..........

Match the columns:

Column $I$	Column $II$
$(a)$ Sickle cell anaemia	$(p)$ Homogentisic acid
$(b)$ Alkaptonuria	$(q)$ Lack of Melanin
$(c)$ Albinism	$(r)$ Accumulation of Amino acid
$(d)$ Phenylketonuria	$(s)$ Defective haemoglobin

Which of the following is a dominant trait?

Identify the correct and incorrect statements from the following:
$(1)$ Mendel is considered the father of modern genetics.
$(2)$ Down's syndrome is a sex-linked chromosomal disorder.
$(3)$ Sickle cell anemia is an example of point mutation.
$(4)$ Color blindness is a hereditary trait.
$(5)$ Triploid female flies are found in Drosophila.

In an organism,pink spot is a sex-linked recessive trait and black hair is dominant to white. If a pink spotted black heterozygous female is mated to a white male which is not spotted,the phenotypic ratio of the offspring would be