Question

Genetics questions, i need help!

1) For the Drosophila red/white cross, you crossed red females and white males (w'w, wy). a) Draw the Punnett Square for this cross (F1). What is the ratio of red females:red males? b) Suppose in the F1 generation, you observed 70 red females and 30 red males. Do a Chi- Square Test to test the hypothesis of the ratio you found in part (a) above. Do you accept or reject the hypothesis? c) Draw the Punnett Square for the F2 generation using the genotypes for the males and female offspring you obtained in part (a) above. What is the ratio of red flies:white flies? d) Suppose in part (c) above, you observed 75 red flies and 25 white flies. Do a Do a Chi-Square Test to test the hypothesis of the ratio you found in part (c) above. Do you accept or reject the hypothesis? 2) For the Drosophila red/white cross, you also crossed white females and red males (ww, wY). a) Draw the Punnett Square for this cross (F1). What is the ratio of red females:white males? b) Suppose in the F1 generation, you observed 50 red females and 60 white males. Do a Chi- Square Test to test the hypothesis of the ratio you found in part (a) above. Do you accept or reject the hypothesis? c) Draw the Punnett Square for the F2 generation using the genotypes for the males and female offspring you obtained in part (a) above. What is the ratio of red flies:white flies? d) Suppose in part (C) above, you observed 75 red flies and 25 white flies. Do a Do a Chi-Square Test to test the hypothesis of the ratio you found in part (c) above. Do you accept or reject the hypothesis? 3) Suppose you counted all your flies and your ratios were off. What could some of the reasons be for your numbers of offspring deviating from your expected ratios? 4) We know that Drosophila is a model organism. Search the web and list how Drosophila has been used to study human diseases.

Answer 1

1.

a.

Red female & white male wiwt wY 1. Wt WT 3 ผ wto el evale y / Wty Wty Red male Wt is wild and is dominant. w is recessere.

All offspring are red. Both males and females are red.1 :1 ratio of male and female.

b.

If there are 100 offspring, 50 of them have to be red males and 50 red females .

chi-square = K²= {CO-E² 6=E32 phenotage obferved Expected C-E) (o-ej2 Red male 30 501-20 2 Red female 70 | 50 +20 400 400.8 50 400 I chi-square: 8+8=16 P=3.84

We reject the hypothesis because chi-square is much higher than the P value.

c.

- Wtw x wty -F, parents wt ~ wt Ì . - WtW wtwt Red WtW / female / Red-3 y Wty/wy wty - Red male te WY- white male-1 Red flies : white flies = 3:1 Wtut

d.

chi-Square = 32= 36-) phenotype de prved Frosted 0-E) (0-3) 2 TM E12 750 Ò | Red offspring while offpring 25 125 0 Ò df= 1 chi-square: 0 P value - 3.84

Here there is no difference between the expected and observed at all. So, we accept the Null hypothesis.