Which of the following is not a sex-linked trait?

The number of chromosomes present in a gorilla is:

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.

Genes that are similar in phenotypic effect when present separately,but together interact to produce a different trait and the ratio is $9:7$ in the $F_2$ generation. What are such genes known as?

Variation stands for differences in traits of progenies from

In a cross between genotypes showing recessive epistasis,the $F_2$ phenotypic ratio will be .....