Lab Writeup for Virtual Flylab I
Problem 1: Investigate the purple eye trait
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Results of Cross #1
Ignoring Sex
Parents
(Female: PR) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 998 1.0000 1.000
Total 998
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A cross of a purple eyed female with wild-type (+) male gave all wild-type (+). My
hypothesis is that purple
eyes is a standard recessive mendelian trait. If so, the genotype of the
purple eyed female was prpr and the genotype of the wild-type male was pr+pr+. Therefore
the F1 wild type progeny should all have the genotype prpr+. If so, a cross of the
F1 should give a 3:1 ratio of wt:purple eyes.
Results of Cross #2
F1 (Female: +) x (Male: +)
prpr+ x prpr+
F2 Offspring
Phenotype Genotype Number Proportion Ratio
+ prpr+ or pr+pr+ 751 0.7327 2.741
PR prpr 274 0.2673 1.000
Total 1025
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As there was no difference between the sexes I've combined the male and
female numbers. The ratio of 751 wt : 274 purple is close
to the predicted 3:1 so I'm going to tentatively accept my hypothesis (boy, I
wish I knew how to do a statistical test to prove this, maybe next week). The
genotype of the purple F2 flies should be prpr while the wt F2 flies should be
a mixture of pr+pr+ and prpr+. As the wt F2 are a mixture, I think I'll test
my hypothesis that the F1 are all prpr+ with a couple of backcrosses. First
I'll cross a wt F1 with a wt parent. As this will be prpr+ x pr+pr+ all of
the progeny will get a pr+ allele and they all should be be wt.
Results of Cross #3
F1 (Female: +) x Parent (Male: +)
prpr+ x pr+pr+
Backcross Offspring
Phenotype Genotype Number Proportion Ratio
+ prpr+ or pr+pr+ 975 1.0000 1.000
Total 975
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I couldn't find my original wt male (must have flew off), so I got another
one from the stock, they're true breeding so the stocks all have the same
genotype. The result was as expected, all wt progeny, so the wt allele is
dominant. This cross really didn't tell me very much so I'll try the
back-cross to the purple eyed parent. As that parent should be prpr this will
be a test cross, F1 prpr+ x Parent prpr, and should give a 1:1 ratio of
purple:wt progeny. As I haven't seen this ratio yet being able to predict a
new result like that will be very strong evidence that my hypothesis is
correct.
Results of Cross #4
F1 (Female: +) x Stock (Male: PR)
prpr+ x prpr
Offspring
Phenotype Genotype Number Proportion Ratio
+ prpr+ 463 0.4889 1.000
PR prpr 484 0.5111 1.045
Total 947
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Yes! As predicted I got a 1:1 ratio of purple:wt. The purple flies must be
prpr and the wt flies should all be prpr+. I repeated the initial crosses
with the sexes reversed and got the same results (data not shown). I conclude
from the disappearance of purple in the F1, the 3:1 ratio of wt:purple in the
F2, and the 1:1 ratio in the wt F1 cross with a purple-eyed fly, that purple
eyes are a standard recessive Mendelian trait.
Problem 2: Investigate the shaven bristles trait
Results of Cross #1
Parents
(Female: SV) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
Female: + 523 0.5034 1.014
Male: + 516 0.4966 1.000
Total 1039
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Hmm, looks like the previous cross, with shaven recessive to wild type. If so the F2 should give a 3:1 ratio of wild type to shaven
Results of Cross #2
Ignoring Sex
Parents
F1 (Female: +) x (Male: +)
Offspring
F2
Phenotype Genotype Number Proportion Ratio
+ ++, +sv 777 0.7493 2.988
SV svsv 260 0.2507 1.000
Total 1037
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Yep, that looks like a 3:1, a test cross of one of the shaven flies to one of the wild type F1 should give me a 1:1 ratio.
Results of Cross #3
Ignoring Sex
Parents
(F1 Female: +) x (Male: SV)
Offspring
Phenotype Geneotype Number Proportion Ratio
+ +sv 497 0.5056 1.023
SV svsv 486 0.4944 1.000
Total 983
Conclusion: As a cross of true breeding wild type with true breeding shaven produce all wild type progeny shaven is recessive. No differences between the sexes so shaven is autosomal. as predicted the F2 gave a 3:1 ratio of +:Sv and crossing the wild type F1 with a shaven flie produced a 1:1 ratio. Shaven is an autosomal recessive trai.
Problem 3: Invetigate the forked bristles trait.
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Results of Cross #4
Parents
(Female: F) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
Female: + 503 0.4951 1.000
Male: F 513 0.5049 1.020
Total 1016
Odd, the males are forked and the females are wild type. I can't tell which trait is dominant. If one of the parents were heterozygous I would have seen a 1:1 ratio like this, but why would it be different in the sexes? and why did the trait switch from females to males? I'll try the F2 cross and see what happens, maybe forked will switch back to the females?
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Results of Cross #5
Parents
(Female: +) x (Male: F)
Offspring
Phenotype Number Proportion Ratio
Female: + 270 0.2695 1.120
Male: + 241 0.2405 1.000
Female: F 245 0.2445 1.017
Male: F 246 0.2455 1.021
Total 1002
Now a 1:1 ratio between forked and wild type and the ratios are the same in the two sexes! this looks like a test cross but I still don't know which trait is recessive! I'll guess that forked is the recessive trait, in which case a cross of the forked flies above should give all forked progeny.
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Results of Cross #6
Parents
(Female: F) x (Male: F)
Offspring
Phenotype Genotype Number Proportion Ratio
Female: F ff 524 0.5107 1.044
Male: F ff? 502 0.4893 1.000
Total 1026
Yes, so the forked flies are homozygous for forked and forked is recessive. cross #5 above gave a 1:1 raito because it was a test cross. therefore the female was heterozygous, which makes sense for a F1 fly. but why were the male F1s forked? They should have been heterozygous also, and thus wild type, yet they appear to be homozygous for forked. Maybe this trait is X-linked and the males are hemizygous. I'll try the whole thing over only with the sexes switched and see if that works. I should see all wild type in the F1
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Results of Cross #7
Parents
(Female: +) x (Male: F)
Xf+Xf+ XfY
Offspring
Phenotype Geneotype Number Proportion Ratio
Female: + Xf+Xf 496 0.4950 1.000
Male: + Xf+Y 506 0.5050 1.020
Total 1002
As expected all wild type, just as with an autosomal cross. In the F2, however, I should see a 3:1, but with only forked males (1:1 in the males)
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Results of Cross #8
Parents
(Female: +) x (Male: +)
Xf+Xf Xf+Y
Offspring
Phenotype Geneotype Number Proportion Ratio
Female: + Xf+Xf+, Xf+Xf 513 0.5049 2.060
Male: + Xf+Y 254 0.2500 1.020
Male: F XfY 249 0.2451 1.000
Total 1016
Yes, just as I predicted, only males are forked. A cross of the F1 female with one of the forked males should produce a 1:1 in both sexes.
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Results of Cross #9
Parents
(Female: +) x (Male: F)
Xf+Xf XfY
Offspring
Phenotype Genotypes Number Proportion Ratio
Female: + Xf+Xf 254 0.2527 1.090
Male: + Xf+Y 255 0.2537 1.094
Female: F Xf+Xf+ 233 0.2318 1.000
Male: F XfY 263 0.2617 1.129
Total 1005
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Results of Cross #10
Ignoring Sex
Parents
(Female: L) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
L 1007 1.0000 1.000
Total 1007
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Results of Cross #11
Ignoring Sex
Parents
(Female: L) x (Male: L)
Offspring
Phenotype Number Proportion Ratio
+ 259 0.2587 1.000
L 742 0.7413 2.865
Total 1001
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Results of Cross #12
Ignoring Sex
Parents
(Female: L) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 479 0.4878 1.000
L 503 0.5122 1.050
Total 982
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Results of Cross #13
Parents
(Female: B) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
Female: B 514 0.5130 1.053
Male: B 488 0.4870 1.000
Total 1002
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Results of Cross #14
Parents
(Female: B) x (Male: B)
Offspring
Phenotype Number Proportion Ratio
Male: + 251 0.2493 1.000
Female: B 501 0.4975 1.996
Male: B 255 0.2532 1.016
Total 1007
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Results of Cross #15
Parents
(Female: +) x (Male: B)
Offspring
Phenotype Number Proportion Ratio
Female: B 481 0.4829 1.000
Male: + 515 0.5171 1.071
Total 996
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Results of Cross #16
Parents
(Female: B) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
Female: + 241 0.2326 1.000
Male: + 266 0.2568 1.104
Female: B 270 0.2606 1.120
Male: B 259 0.2500 1.075
Total 1036
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Results of Cross #17
Parents
(Female: B) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
Female: + 244 0.2438 1.030
Male: + 237 0.2368 1.000
Female: B 257 0.2567 1.084
Male: B 263 0.2627 1.110
Total 1001
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Results of Cross #18
Ignoring Sex
Parents
(Female: CY) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 497 0.4980 1.000
CY 501 0.5020 1.008
Total 998
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Results of Cross #19
Ignoring Sex
Parents
(Female: +) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 1001 1.0000 1.000
Total 1001
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Results of Cross #21
Ignoring Sex
Parents
(Female: CY) x (Male: CY)
Offspring
Phenotype Number Proportion Ratio
+ 346 0.3443 1.000
CY 659 0.6557 1.905
Total 1005
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Results of Cross #22
Ignoring Sex
Parents
(Female: +) x (Male: CY)
Offspring
Phenotype Number Proportion Ratio
+ 537 0.5163 1.068
CY 503 0.4837 1.000
Total 1040
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