Question

Red and tall dominant character hybrid plant when crossed with the recessive white dwarf plant(RrTt X rrtt), what will be the ratio of respective four combinations, red tall, red dwarf, white tall and white dwarf plants in the next generation?
A. 9:3:3:1
B.15:1:0:0
C. 9:3:4:0
D. 4:4:4:4

Answer 1

Hint: Inheritance of two traits at a time is called Dihybrid cross. Plant with genotype RrTt will produce four different combinations of gametes, i.e. RT, Rt, rT and rt. The other plant with genotype rrtt will produce only one type gamete which is rt.

Complete step by step answer: The inheritance of two traits at a time is called dihybrid cross. Plant with genotype RrTt will produce four different combinations of gametes, i.e. RT, Rt, rT and rt.
The other plant with genotype rrtt will produce only one type gamete which is rt.
A cross obtained between RrTt and rrtt; we get:

Gametes	RT	Rt	rT	rt
rt	RrTt	Rrtt	rrTt	rrtt
	Red, tall	Red, dwarf	White, tall	White, dwarf

Note: When similar hybridization experiments were conducted in another plant, it was found that in some plants, F1 generation had phenotypes that did not resemble either of the two parents. Such F1 hybrids were showing incomplete dominance. Incomplete dominance is a partial expression of alleles in the heterozygous condition so that a hybrid shows an intermediate phenotype instead of one of the parent type. The genotypic ratio of such cross is 1:2:1 and phenotypic ratio is 1:2:1. For example the flower colour in Mirabilis jalapa.