Question

Differentiate between:

monohybrid and dihybrid cross (phenotypic ratio) 

Answer 1

	Monohybrid cross	Dihybrid cross
1.	It involves a cross between two organisms differing in one trait.	It involves a cross between two organisms differing in two traits.
2.	The progeny obtained from the monohybrid cross is called the monohybrid species.	The species obtained from the dihybrid cross is called dihybrid species.
3.	It is used to study the inheritance of a single pair of alleles.	It is used to study the inheritance of two different alleles.
4.	It is used to study the dominance of species.	It is used to study offspring assortment.
5.	Example: Cross between Tt x TH (T = tall t = short)	Example: Cross between RrYy x RrYy (R = round, = wrinkled; Y = yellow, y = green)
6.	The phenotypic ratio is : 3 : 1	The genotypic ratio is 9 : 3 : 3 : 1
7.	The genotypic ratio is: 1 : 2 : 1	The phenotypic ratio is 1 : 2 : 1 : 2 : 4 : 2 : 1 : 1
8.	The cross test ratio is 1 : 1	The test cross ratio is 1 : 1 : 1 : 1