Help Biology SAC

[ladyy]

How do you prove that two genes are located on the same chromosome.

In my case in relation to corn kernels

Sweet/Starchy
Purple/Colourless

[Jdog]

you cant really prove it with just experimental evidence, but you can suggest it via the ratios you recieve which may be similar to genes that are not linked.

[ladyy]

So would I suggest it with the ratios?

So If I got a 3:1 ratio for both phenotypes, I could say they are not linked

sorry if i sound stupid :\

[jasoN-]

hmm, I don't think they'll ask how to prove for that.
Theoretically you could show that if the ratios are approx 9:3:3:1 (typical dihybrid cross) then the genes are located on the same chromosome. But of course in reality, anything could happen as it is by chance.

I did this sac not too long ago, there wasn't any question proving.
I had a ratio of ~113:29:31:13(can't remember exactly), so it's approx the typical ratio.

As the typical dihybrid cross assumes they are on the same gene and the actual ratio is roughly the same, they are on the same gene.

And yeah if you get something like 3:1 ratios for both the phenotypes, you could say they are most likely not linked (as I said, can't be certain due to chance)

[ladyy]

thanks so much, i get it now

[Russ]

can't be certain due to chance

Perfectly true, which is why p values are quoted for experiments done and we accept it as proof if it's below an arbitrary level.

But yes, sequencing the chromosome is the only way to know for certain.

So If I got a 3:1 ratio for both phenotypes, I could say they are not linked

In your answer you should note that they could still be on the same chromosome but >50mu apart