How do you create a dihybrid cross?

check these out!

http://en.wikipedia.org/wiki/Dihybrid_cross

www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cross/03Q.html

science.nhmccd.edu/Biol/dihybrid/dihybrid.html

www.geocities.com/CapeCanaveral/Hall/1410/lab-B-20.html


     RB Rb rB rb
RB RRBB RRBb RrBB RrBb
Rb RRBb RRbb RrBb Rrbb
rB RrBB RrBb rrBB rrBb
rb RrBb Rrbb rrBb rrbb

Ratio: 9:3:3:1

RR
rR
BB
bB

You must use a Punnett square to calculate the traits to make sure you do it right.

It is the same concept as a monohybrid cross, but you will have four possible genotypes across each side. For RrBb: RB, Rb, rB, rb. For RRBB: RB, RB, RB, RB. You basically just write each possible combination and write one set across the top and one across the side. You'll end up with sixteen boxes instead of four, but it's the same concept - don't make it harder than it is. I hope this made sense!

okok wat u do is make a punnett square. one side has RB, Rb, rB, and rb.  The top will have RB, RB, RB, RB. Then multiply.

              RB    RB    RB   RB
              ---------------------------------
       RB  [     ][      ][         ][      ]
       Rb  [     ][      ][        ][      ]
       rB   [     ][      ][         ][     ]
       rb   [     ][       ][        ][      ]

you cross the numbers like any punnet square.
There are four colums on each side. so the top numbers are
1) RB      2)Rb      3) rB     4) rb
Going down.
1)RB
2)RB
3)RB
4)RB
There is going to be for digits in one box. there should be 16 boxes all thogether. The fist box is going to be RRBB. The second going to the right is going to be RRBb. Ther third one is going to be RrBB. the fourth box is going to be RrBb. you do the rest. It's sort of fun once you get the hang of it.

You make a square with 16 boxes
Two capital letters are dominate and a capital and lower case letter is a carrier and two lower case letter are recessive
so if your parents are
RrBb and RRBB  you would take the first and the third and then the first and the fourth and then the second and the third and then the take the second and the fourth
put one parent across the top and one parent along the left side
Then your box with have the parents and you look at the first parent on the top and then you take those two letters and then look at the first parent on the side and take those to letters and put them in the first box and keep doing that all the way along  and when you finish all of the boxes based on the information i told you at the top you will be able to figure out the genotypes and the offsprings