1. Kohshi Gokita
IB Biology HL Per. 5
Fly Lab
Introduction:
In this investigation of fly lab, this is based on genetics and gives realistic ratios when crosses are
performed. This lab was according to Thomas Hunt Morgan, so you must be like real geneticist
to work on this lab. At first, you have to find for dominant allele, which is powerful gene in
crossing. So the appearances or features are often be same as dominant gene’s features. On the
other hand, there is another type of allele, called recessive. It is weaker than dominant. All the
appearance of organism are referred in phenotype, which expresses how the organisms look like.
And genotype expresses traits of alleles. According to Mendel, the gene which contains two
same alleles are called homozygous, and the off springs which are produced from homozygous
pairs are called F1 generation. From the F1 generation, the gene which contains different alleles
are produced and they are called heterozygous. And if you cross the F2 generation, it is expected
that the ratio of off spring will be 3:1 in monohybrid cross. In dihybrid cross, the ratio of 9:3:3:1
is expected. Thus, in this investigation, you find dominant alleles, recessive alleles, sex-linked
recessive alleles, dihybrid allele, and dominant lethal allele. And you check the reliability of the
data by using chi-square.
Data Collections (total 5 crosses alleles)
Dominant Allele: Wild vs. Eye Shape Lobe
F1 generation
Results of Cross #1
Ignoring Sex
Parents
(Female: L) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
L 1018 1.0000 1.000
2. Total 1018
*According to data, it shows that eye shape lobe fly mated with wild type eye shape. It reveals
that the gene of eye shape lobe is dominant allele over gene of wild type eye shape because that
off spring of F1 generation are all fly of eye shaped lobe.
L=eye shape lobe
+=wild type
LL x ++
+ +
L L+ L+
L L+ L+
Genotype = L+
Phenotype = all’s eye shapes are lobe.
F2 generation
Results of Cross #2
Ignoring Sex
Parents
(Female: L) x (Male: L)
Offspring
Phenotype Number Proportion Ratio
+ 242 0.2490 1.000
L 730 0.7510 3.017
3. Total 972
Chi Square Hypothesis Using Cross #4
Ignoring Sex
Phenotype Observed Hypothesis Expected Chi-Square Term
+ 242 710.0000 690.1200 290.9806
L 730 290.0000 281.8800 712.4008
Total 972 1000.0000 972.0000 1003.3814
Chi-Sqaured Test Statistic = 1003.3814
Degrees of Freedom = 1
Level of Significance = 0.0000
Recomendation: Reject your hypothesis
*Finally, it supported that eye shape lobe is dominant allele over wild type eye shape. In the
F1generation, all of the genotypes were heterozygous of L+. L is dominant over +, so all the
phenotypes in F1 generation became eye shaped lobe. However, in F2 generation, to cross with
the two heterozygous genes of L+, the off spring becomes eye shaped lobe fly and wild type eye
shape. So the ratio is 3:1.
L+ x L+
L +
L LL L+
+ L+ ++
Genotype = LL: L+ : ++ = 1:2:1
4. Phenotype = eye shape lobe : eye shape lobe : wild type
Recessive allele: Wild vs. Incomplete wing vein
F1 generation
Results of Cross #1
Ignoring Sex
Parents
(Female: RI) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 941 1.0000 1.000
Total 941
*According to data, it shows that type of incomplete wing vein mated with wild type wing vein.
It reveals that the gene of incomplete wing vein is recessive allele under gene of wild type wing
vein because that off spring of F1 generation are all wild type wing vein.
RI = incomplete wing vein
+ = wild type wing vein
RIRI x ++
RI RI
+ +RI +RI
+ +RI +RI
Genotype = +RI
5. Phenotype = wild type wing vein
F2 generation
Results of Cross #2
Ignoring Sex
Parents
(Female: +) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 763 0.7502 3.004
RI 254 0.2498 1.000
Total 1017
Chi Square Hypothesis Using Cross #2
Ignoring Sex
Phenotype Observed Hypothesis Expected Chi-Square Term
+ 763 700.0000 711.9000 3.6679
RI 254 300.0000 305.1000 8.5585
Total 1017 1000.0000 1017.0000 12.2265
Chi-Squared Test Statistic = 12.2265
Degrees of Freedom = 1
6. Level of Significance = 0.0005
Recommendation: Reject your hypothesis
*Finally, it supported that incomplete wing vein is recessive allele under wild type wing vein. In
the F1generation, all of the genotypes were heterozygous of +RI. + is dominant over RI, so all
the phenotypes in F1 generation became wild type wing vein. However, in F2 generation, to
cross with the two heterozygous genes of +RI, the off spring becomes incomplete wing vein fly
and wild type wing vein. So the ratio is 1:3.
+RI x +RI
+ RI
+ ++ +RI
RI +RI RIRI
Genotype = ++ : +RI : RIRI = 1:2:1
Phenotype = wild type wing vein to incomplete wing vein = 3:1
Recessive sex-linkedallele: Wild vs. forked bristle
F1 generation
Results of Cross #1
Parents
(Female: +) x (Male: F)
Offspring
Phenotype Number Proportion Ratio
Female: + 476 0.4779 1.000
Male: + 520 0.5221 1.092
Total 996
7. *According to data, it shows that forked bristle fly mated with wild type bristle. It reveals that
the gene of forked bristle is recessive allele under gene of wild type bristle because that off
spring of F1 generations are all wild type bristle.
+ = wild type bristle
F = shaven bristle
++ x FF
+ +
F +F +F
F +F +F
Genotype = +F
Phenotype = wild type bristle
F2 generation
Results of Cross #2
Parents
(Female: +) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
Female: + 518 0.5005 2.072
Male: + 267 0.2580 1.068
Male: F 250 0.2415 1.000
Total 1035
8. Chi Square Hypothesis Using Cross #6
Phenotype Observed Hypothesis Expected Chi-Square Term
Female: + 518 500.0000 517.5000 0.0005
Male: + 267 250.0000 258.7500 0.2630
Male: F 250 250.0000 258.7500 0.2959
Total 1035 1000.0000 1035.0000 0.5594
Chi-Sqaured Test Statistic = 0.5594
Degrees of Freedom = 2
Level of Significance = 0.7560
Recomendation: Do not reject your hypothesis
*Finally, it supported that forked bristle is recessive allele under wild type bristle. And it can be
also defined in sex linkage. In the F1generation, all of the genotypes were heterozygous of +F. +
is dominant over F, so all the phenotypes in F1 generation became wild type bristle. However, in
F2 generation, to cross with the two heterozygous genes of +F, the only male off spring became
forked bristle. So, it represents that female is carrier of the gene of forked. Female off springs do
not become forked bristle.
Female +F x Male +F
X+ XF
X+ X+X+ X+XF
YF X+YF XFYF
Genotype = X+X+ : X+XF : X+YF : XFYF = 1 : 1 : 1 : 1
Phenotype = female wild : male wild : male forked bristle = 2 : 1 : 1
9. Dihybrid allele: Wild vs. eye shape Lobe and bristle Forked
F1 generation
Results of Cross #1
Ignoring Sex
Parents
(Female: +) x (Male: F;L)
Offspring
Phenotype Number Proportion Ratio
L 1028 1.0000 1.000
Total 1028
Explanation:
According to data, male fly which contains gene of forked bristle and lobe eye shape mated with
wild type female fly. This data shows that the forked and love are dihybrid cross. It is because
that heterozygous genes are crossed together.
+= wild type body color
FL= curve and incomplete
+C x FLFL
+ +
FL FL+ FL+
FL FL+ FL+
Genotype of the offspring = FL+
Phenotype of the offspring = eye shape lobe
10. F2 generation
Results of Cross #2
Ignoring Sex
Parents
(Female: L) x (Male: L)
Offspring
Phenotype Number Proportion Ratio
+ 180 0.1818 2.769
F 65 0.0657 1.000
L 543 0.5485 8.354
F;L 202 0.2040 3.108
Total 990
Chi Square Hypothesis Using Cross #10
Ignoring Sex
Phenotype Observed Hypothesis Expected Chi-Square Term
+ 180 200.0000 198.0000 1.6364
F 65 100.0000 99.0000 11.6768
L 543 500.0000 495.0000 4.6545
F;L 202 200.0000 198.0000 0.0808
Total 990 1000.0000 990.0000 18.0485
11. Chi-Sqaured Test Statistic = 18.0485
Degrees of Freedom = 3
Level of Significance = 0.0004
Recomendation: Reject your hypothesis
Explanation:
According to the data, it proved that lobe eye shape and forked bristle are dihybrid cross. In F1
generation, the phenotypes are all forked bristle but in F2 generation, the ratio of wild type, lobe
eye shape, and forked bristle became 9:3:3:1.
F = Forked bristle
L = lobe eye shaped
FfLl x FfLl
FL Fl fL fl
FL FFLL FFLl FfLL FfLl
Fl FFLl FFll FfLl Ffll
fL FfLL FfLl ffLL ffLl
fl FfLl Ffll ffLl Ffll
Genotype =FFLL : FFLl : FfLL : FFll : FfLl : ffLL : Ffll : ffLl : ffll = 1: 2:2:1:4:1:2:2:1
Phenotype = lobe/forked : lobe : forked : wild type =9:3:3:1
Dominant lethal allele: Aristapedia male vs. Aristapedia female
F1 generation
Results of Cross #1
12. Ignoring Sex
Parents
(Female: AR) x (Male: AR)
Offspring
Phenotype Number Proportion Ratio
+ 362 0.3539 1.000
AR 661 0.6461 1.826
Total 1023
*This is the data of male fly with aristapedia antenna and female fly with aristapedia antenna
mated together. This data shows the ratio of wild type and antenna aristapedia, which is 1:2. The
wild type genotype ++ is impossible to produced in this dominant lethal because it refers to death.
AR = Aristapedia
+= wild type
AR+ x AR+
AR +
AR ARAR AR+
+ AR+ ++ death
Genotype = ARAR : AR+ : ++ (death)= 1:2
Phenotype = Aristapedia : wild type = 2:1
F2 generation
Results of Cross #2
13. Ignoring Sex
Parents
(Female: +) x (Male: +)
Offspring
Phenotype Number Proportion Ratio
+ 1019 1.0000 1.000
Total 1019
Chi Square Hypothesis Using Cross #27
Phenotype Observed Hypothesis Expected Chi-Square Term
Female: + 524 500.0000 509.5000 0.4127
Male: + 495 500.0000 509.5000 0.4127
Total 1019 1000.0000 1019.0000 0.8253
Chi-Sqaured Test Statistic = 0.8253
Degrees of Freedom = 1
Level of Significance = 0.3636
Recomendation: Do not reject your hypothesis
*According to data, it reveals that aristapedia male mates with aristapedia female will be
dominant lethal allele. In F1 generation, their dominant allele of wild type kills pair up and died,
so that is why the ratio was 2:1 of aristapedia and wild type, but in F2 generation, the result was
different. The F1 generation crosses together, it produced only wild type off springs.
14. AR= aristapedia
+ = wild type
AR+ x ++
AR +
+ AR+ ++
+ AR+ ++
Genotype = AR+ : ++ = 1:1
Phenotype = aristapedia : wild type = 1:1
Failed Crosses;
Dominant allele wild type vs. star eye shape
Recessive allele-----
Recessive sex-linked allele-----
Dihybrid Crosswild type vs. eye less & curly wing
wild type vs. eye color sepia & miniature wing
wild type vs. body color ebony & aristapedia antenna
Dominant Lethal Alleleeye color brown vs. wing size apeterous
eye shape bar vs. eye color purple
body color yellow vs. wing shape curved
