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A Dihybrid Cross Simplified with an example

Introduction

I will show you a simplified method using a Punnet Square to predict a dihybrid cross when observing the passage of 2 genes.

The traditional Punnet Square using a monohybrid cross is usually quite simple, but you can get confused with dihybrid crosses if you do not understand the laws that govern them. Take a quick look at my article about Mendel’s Laws if you are not familiar with them.

 

A simple example of a dihybrid cross

A simple example of a dihybrid cross we can predict is the breeding of 2 Aliens.  Find the genotype and phenotype of the offspring if both Aliens are heterozygous for beady eyes (E) and green skin (S)?

 

Step 1.  Find the genotype of the parents

Since the parents are heterozygous( different alleles) this means the parents have a genotype:

(Ohmmy3d)freedigitalphotos.net

Ee – for the eyes

Ss – for the skin.

 

 

 

 

 

 

 

Step 2. Fill in the Punnet Square

What the Punnet Square does is list every combination possible. E-S, E-s then e-S, e-s.

Punnet Square Dihybrid Cross

 

How we would use this in real life?

What I didn’t mention is these Aliens landed in New Mexico in 1989, and a baby was about to be born. From what we knew about their species, only Martians with normal eyes (ee) and normal skin (ss) could survive the harsh conditions of our plant. What are the chances their single alien child will survive?

In this case the alien child has a 1 out of 16 chance of surviving. 1 out of the 16 boxes has the combination eess.

 

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One comment

  1. can u please help me with the following cross to find the F1 and F2 generation?
    B> for color which is black
    b> for white color
    L>for long hair
    l>for short hair

    BBLL X BbLl