Biology...dihybrid crossing techniques

[QueHuong]

Drawing a punnet square like this takes too long for a test. I'm sure there are quick and dirty ways to compute all the different possible combinations of crossing, like by FOILing (such as the one you learn in math). But I'm not exactly sure how to go about that. So can someone show me how to quickly cross genes, for example:

AaBb x AaBb

 

[jacob0401]

you can split the traits up into two regular 4 square punnets...let's say you're looking at A and B traits.... AaBb AaBb

Then you multiply the probabilites from one punnet to the other...

So have one Aa * Aa punnet and another Bb * Bb punnet...let say you want the phenotype A_B_ (homozygous dominant) you look how many in the A punnet fit that criteria of A_(dominant) it should be 3/4, and then you look to the B punnet and see how many fulfill B_(dominant), it sohuld be 3/4. Then you multiple the two probabilites and you get 9/16, which is the correct ratio for A_B_.

 

[Mallow]

there are computer programs that will compute the gamete ratios.

 

[jacob0401]

Originally posted by: Mallow
there are computer programs that will compute the gamete ratios.

Yeah there are, but that won't be good for a test...and its not exceedingly difficult

 

[MrCodeDude]

That's the easiest way to do it, just keep practicing over and over and you'll be able to do those problems in like less than 1 minute.
-- mrcodedude

 

[chiwawa626]

remember popular ratios and what the genotypes look like

W00t got an A in ap bio!