Genetics problem, I am stuck

[jacss2]

Hello,

I want to study the inheritance of red eyes and white eyes in drosophila.
I have mated red-eyed females with white eyed males.

F1: F1: All F1 females were white eyed and all F1 males were red-eyed.
19 white eyed females and 22 red eyed males.

I have also crossed the females and males of the F1 generation, but this is not relevant for my question.

I am trying to draw a pedigree chart for the P generation and their offspring, but there is a small problem. I know that this trait is sex-linked, and that the white eyes allele is recessive. Let R denote the red eyes allele and r the white eyes allele. Here is what I get:



Can someone please explain me the problem.
Thank you very much

[JackBean]

why the mother can't be heterozygous?

[jacss2]

Hello

The teacher told us the females of the P generation is homozygous. However, maybe she was wrong. I guess you are saying this because it is impossible to get these data without the mother being heterozygous?

[JackBean]

well, you could come up with some mutation or gene expression alteration... but that had to occur already in mother's ovaries or what do flies have, as all offspring is the same

[fastsandslash]

Yes, the only way apart from mutations, would be a heterozygous mother since the male has only a recessive r, and the female must have another recessive r (as a female offspring has rr=red eyes), thus, the genotype of the mother must be Rr or else there will be no recessive phenotyped children. (add punnet square here)

[zuzike]

Hi, maybe there is problem with cultivation temperature. There has been one experiment in Swiss, where drosophila eggs were cultivated in different temperature and the color of their eyes has changed.

[jasmine25]

Can anyone explain me the problem of red eyes and white eyes

[JackBean]

Hi, maybe there is problem with cultivation temperature. There has been one experiment in Swiss, where drosophila eggs were cultivated in different temperature and the color of their eyes has changed.

yeah, I think some silencing... however, question is, whether it would occur in all females?

[zuzike]

JackBean: Sa mi zda ze tam sa jednalo o epigeneticku zmenu. A nepamatam sa, zeby hovorili o nejakych pomeroch, ale skor, ze sa to stalo u vsetkych.

[JackBean]

však jo, silencing je epigenetická změna způsobená třeba methylací, ať už v promotoru nebo v kódující oblasti.

A pokud to bylo dáno podmínkami, tak je logické, že toho dosáhli u všech. Jenže to nevysvětluje, proč chlapáci měli červený oči