Question

learn how to solve dihybrid cross problems

Answer 1

Dihybrid cross was initiially studied by mendel (in pea plants),and we can easly anlysis it with the help of punnet square.And a dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits.

And we can understand this easly by taking an example.

So let consider an example of cross between pea palnts having traits round yellow seed and wrinkled green seed.

Here the trait shape,round is dominant over wrinkled and trait colour yellow is dominant over green.

So we are representing the genotypes of the round yellow seed as RRYY and wrinkled green as rryy.

Gametes are RY and ry and hence the progenies genotype is RrYy.(this is the F1 generation)

And now we are going to the F2 generation with cross between F1 progenies,that is between two RrYy

That is,

Here the ganetes are RY, Ry, rY, ry

So now we just take the cross with the help of punnet square.( The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach)

**	RY	Ry	rY	ry
RY	RRYY	RRYy	RrYy	RrYy
Ry	RRYy	RRyy	RrYy	Rryy
rY	RrYY	RrYy	rrYY	rrYy
ry	RrYy	Rryy	rrYy	rryy

** male or female gametes.

So here we are getting 9 round yellow,3 round green,3 wrinkled yellow and 1 wrinled green.

[round yellow can be the genotypes RRYY, RrYy, RRYy,RrYY and round green can RRyy, Rryy and wrinkled yellow can rrYy, rrYY and wrinkled green is rryy].

So phenotypic ratio of round yellow:round green:wrinkled yellow:wrikled green is 9:3:3:1.