Mendelian's - epitasis 9:3:4 , biology

[cliffordlim]

After I have done counting the corn and the result 267 yellow , 97 white , 144 purple
ratio 9:3:4 respectively . Recessive - Epitasis ?
I have no idea create a inheritance cross and the biochemical influence by genes interaction from
this phenomena

 

[epenguin]

After I have done counting the corn and the result 267 yellow , 97 white , 144 purple
ratio 9:3:4 respectively . Recessive - Epitasis ?
I have no idea create a inheritance cross and the biochemical influence by genes interaction from
this phenomena

That by itself is not a phenomenon. If I told you the number of books of different colours on my shelves would that be a phenomenon?

You have to state what this corn your counted has come out of. Some cross? The total descendance after n=? generations from two ancestors? Something else?

 

[cliffordlim]

This is the dihybrid cross where the parents are purple ( rrCC ) x white ( RRcc)
F1 generation all RrCc(yellow ).The result is F2 generation in the ratio 9:3:4 . (Yellow:white:purple)
What kind of gene interaction is this and how should I explain it?

 

[epenguin]

I can't say I ever met this sort of situation before, but I found a, repeat a, possible solution so it Is not a question of expertise, just thinking.

9 + 3 + 4 = 16, convenient. Take one gene and the three genotypes are in ratio 1/4: 2/4: 1/4 or 4/16: 8/16: 4/16 . You can probably see where your 4/16 purples are coming from. I wrote out a tree - top layer

RR. Rr. rr
4. 8. 4Then on next layer wrote the three genotypes that come under each of those in F2 with their expected frequencies in sixteenths.

Excluding the purples I looked for what combinations of c/C's do I see 3 of? There seems to be more than one answer, I don't know if there is other information to distinguish these, but getting that far is the main thing.

 

[epenguin]

OP not come back, not recommending self for any future help but I think it is a shame to leave questions unanswered like this when the answer is so simple yet maybe not at first sight obvious.

Point is a bit of familiarity helps a lot with genetics - geneticists can look at quite complicated data and reel you off the explanation just like that while you have to work it out more slowly on paper, in fact I wrote myself out the genotype frequencies as mentioned in #4.

But then I see, just in your head, what can explain 3/16 whites? Simples - first the data indicated that RR makes purple independent of the C locus, but presence of two R necessary for it. That is 4/16 cases, now of the 12 left 3 are white, that's just the expected 1/4 of homozygous for C, when you have 1:2:1 i.e. 3:6:3 of cc:Cc:CC. White recessive.