Login

Join for Free!
119215 members


I need help with a genotype problem ... really bad...

Genetics as it applies to evolution, molecular biology, and medical aspects.

Moderator: BioTeam

I need help with a genotype problem ... really bad...

Postby xcuteJinax3 » Sun Mar 05, 2006 9:20 pm

In fruit flies, the phenotype for eye color is determined by a certain locus. E indicates the dominant allele and e indicates the recessive allele. The cross between a male wild-type fruit fly and a female white-eyed fruit fly (recessive) produced the following offspring.

F1: Wild-type male: 0, wild-type female: 45, white-eyed male: 55, white-eyed female: 0, brown-eyed female: 1.

The wild- type and white -eyed individuals from the F1 generation were then crossed to produce the following offspring.
F2: 23, 31, 22, 24, 0

a) Determine the genotypes of the original parents (P generation).
b) Use a Chi-squared test on the F2 generation data to analyze your prediction of the parental genotypes.



-----------------

I've worked on this large problem for hours and i'm having a lot of trouble with it. I'm not sure how you would find the genotype using punnet squares for letter a, and how i would use a chi squared test for the F2 generation when they only give those numbers, and no progeny, etc...



please help. :shock: THANK YOU
xcuteJinax3
Garter
Garter
 
Posts: 8
Joined: Sun Feb 26, 2006 6:31 am

Postby GreenDog » Mon Mar 06, 2006 10:07 am

The gene is attached to X, the P-male was E/- the P-female was e/e. The female offspring were all E/e and the males were e/-. When crossing the F1 you cross E/e with e/- and get males: E/- red and e/- white, Females E/e red and e/e white. The f1 brown fenale was a new mutation or something ignore it.

If you do the Chi-sqare with the expected of 1:1:1:1 or 25 of each, you'll see that it fits.
"When In Danger Or In Doubt Run In Circles Scream And Shout"
Lawrence J. Peter
User avatar
GreenDog
Coral
Coral
 
Posts: 126
Joined: Sun Mar 27, 2005 8:37 am

Postby xcuteJinax3 » Tue Mar 07, 2006 8:29 pm

Okay I worked out some of teh problem ...the steps I know that are correct ...

Wildtype white eyed

I know that the cross for that is RY x rr, giving a 1:1 ratio. I know that ratio is correct but I don't know why it is RY x rr and I'm also confused on how I would set up the other crosses .


I really need those ratios in order to use a chi squared test to analyze the prediction of the parental genotypes, but I'm really having trouble getting the correct ones, and I'm solved it many times but it never seems to come out correctly. I'm confused. :( Im sorry.


Thank you!!
xcuteJinax3
Garter
Garter
 
Posts: 8
Joined: Sun Feb 26, 2006 6:31 am


Postby GreenDog » Thu Mar 09, 2006 9:35 am

The logic to the solution was: You got fifferent results for male an female - it means that the gene is sex linked.

The males who inherit only from the mother were all white it means that all the mothers wree rr.
but all the females were red it means they had to get the gene from the fater so he was RY, it also explains wht the gene is X linked and not Y linked.

In this cross the females would all be Rr and the males rY.
Just write everything on a piece of paper and you'll see.

for the Chi square as i mentioned (obs-exp)^2 is (23-25)^2+(22-25)^2+(24-25)^2+(31-25)^2 or just use Excel!
"When In Danger Or In Doubt Run In Circles Scream And Shout"
Lawrence J. Peter
User avatar
GreenDog
Coral
Coral
 
Posts: 126
Joined: Sun Mar 27, 2005 8:37 am


Return to Genetics

Who is online

Users browsing this forum: No registered users and 0 guests