dihybrid cross

[angleslam08]

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Hi, could someone tell me why for a dihybrid cross the punnet square is set up the way it is? I look at it and don't understand why it is specifically laid out that way.... i know purpose is to show independent assortment of independent traits on separate chromosomes and blah but I don't get the reason behind why it's WG/Wg/wG/wg specifically.....please enlighten my stupidity. 😳

 

[cbrons]

Hi, could someone tell me why for a dihybrid cross the punnet square is set up the way it is? I look at it and don't understand why it is specifically laid out that way.... i know purpose is to show independent assortment of independent traits on separate chromosomes and blah but I don't get the reason behind why it's WG/Wg/wG/wg specifically.....please enlighten my stupidity. 😳

What do you mean by "setup"? What are the genotypes of the P generation that you are crossing? Or just give us the entire question so maybe we can understand what you're trying to figure out.

 

[angleslam08]

Ah, sorry. I didn't realize i was so unclear in my description. I mean basically if you wanted to do a dihybrid cross starting with an empty box, how would you go about doing it.

http://www.biologycorner.com/resources/dihybrid_cross.gif

How do you know to set up RY/Ry/ry/rY in that order* across the top and down the left margin to determine the 9:3:3:1 ratio. is it arbitrary? Now that I look at a few different examples I think it is, it seems you just have one of every combination of the two alleles(?).

 

[cbrons]

Right... those are just possible gametes. The 9/3/3/1 is the Mendelian ratio.

 

[Silverfalcon]

If your question is about how to set the Punnet Square up, this may help:

http://anthro.palomar.edu/mendel/mendel_2.htm

 

[howyoudoin]

Not sure i understand your question but this is just to vary the possibility in assortment of seperate traits together You might use the fork line method it helps understand.

EX. WG are the phenotypes Capital being domanate. Then the variations that can be seen are WG/Wg/wG/wg or domanate domanate / Domanate recessive/recessive domanate. ect