Answer: Two Yellow colored and two ebony colored fruit flies are provided as mentioned in the question. It is not known to us, of them, which one is the dominant trait for the body color character. Case 1: Cross #1 Yellow colored fruit flies are crossed with ebony colored fruit flies and as a result all progeny obtained in the F1 generation are of a single color- Ebony. This observation leads to the impression that Ebony coloration is the dominant trait whereas Yellow is the recessive trait. Both the parents are homozygous for the trait and are pure breeding varieties. If that would not have been the case, in the F1 generation itself two variants- both Ebony and Yellow colored progeny would have appeared. According to Mendelian laws, Let, \'Y\' be the factor responsible for Ebony coloration and \'y\' be the factor responsible for Yellow coloration. Thus, in the parental generation, Genotype of the parent having Ebony coloration (homozygous pure breeding variety) - YY Genotype of the parent having Yellow coloration (homozygous pure breeding variety) - yy Hence, genotype of the progeny in F1 generation - Yy Case 2 : Cross #2 In the present case it was observed that 113 Yellow fruit flies were obtained and 120 Ebony fruit flies were obtained in the F1 generation as a result of a cross between an ebony & another yellow fruit fly. So, in the F1 generation, both the variants were obtained almost approximately in 1:1 phenotypic ratio. Since both the variants were obtained, it may be concluded that parent bearing ebony coloration was heterozygous whereas the yellow colored fly was a pure breeding variety. Thus, Genotype of the parent having Ebony coloration - Yy (heterozygous) Genotype of the parent having Yellow coloration -yy (homozygous) Ebony colored parent gives rise to two types of gametes- one bearing \'Y\' factor and the other bearing \'y\' factor. Yellow colored parent gives rise to only gametes bearing \'y\' factor. Gametes Y y y Yy (heterozygous ebony) yy (homozygous yellow) y Yy yy Progeny obtained in the F1 generation have genotype Yy ( heterozygous ebony) and yy(homozygous yellow). Case 3: Cross #3 Two ebony offspring are crossed having genotype \'Yy\'. Genotype of the progeny in F2 generation can be obtained by using checkerboard- Gametes Y y Y YY (homozygous Ebony) Yy (heterozygous ebony) y Yy (heterozygous ebony) yy (homozygous yellow) Thus, phenotypic rato between Ebony & Yellow colored fruit fly -3:1 (Ebony: Yellow) Genotypic ratio in F2 generation - YY: Yy : yy - 1: 2: 1 Case 4 :Cross #4 Mating is performed between Ebony colored fruit fly #3 having genotype \'Yy\' and Ebony colored fruit fly #2 having genotype \'YY\'. #3 ebony colored fly gives rise to to different types of gametes- one bearing \'Y\' allele and the other bearing \'y\' allele for body color character. The genotype and the phenotype of the progeny in this case can be obtained using checkerboard. Gametes Y y Y YY ( homozygous ebony) Yy (heterozygous ebony) Y YY Yy Th.

1. Answer:
Two Yellow colored and two ebony colored fruit flies are provided as mentioned in the question.
It is not known to us, of them, which one is the dominant trait for the body color character.
Case 1: Cross #1
Yellow colored fruit flies are crossed with ebony colored fruit flies and as a result all progeny
obtained in the F1 generation are of a single color- Ebony. This observation leads to the
impression that Ebony coloration is the dominant trait whereas Yellow is the recessive trait.
Both the parents are homozygous for the trait and are pure breeding varieties. If that would not
have been the case, in the F1 generation itself two variants- both Ebony and Yellow colored
progeny would have appeared.
According to Mendelian laws,
Let, 'Y' be the factor responsible for Ebony coloration and 'y' be the factor responsible for
Yellow coloration.
Thus, in the parental generation,
Genotype of the parent having Ebony coloration (homozygous pure breeding variety) - YY
Genotype of the parent having Yellow coloration (homozygous pure breeding variety) - yy
Hence, genotype of the progeny in F1 generation - Yy
Case 2 : Cross #2
In the present case it was observed that 113 Yellow fruit flies were obtained and 120 Ebony fruit
flies were obtained in the F1 generation as a result of a cross between an ebony & another yellow
fruit fly. So, in the F1 generation, both the variants were obtained almost approximately in 1:1
phenotypic ratio. Since both the variants were obtained, it may be concluded that parent bearing
ebony coloration was heterozygous whereas the yellow colored fly was a pure breeding variety.
Thus,
Genotype of the parent having Ebony coloration - Yy (heterozygous)
Genotype of the parent having Yellow coloration -yy (homozygous)
Ebony colored parent gives rise to two types of gametes- one bearing 'Y' factor and the other
bearing 'y' factor. Yellow colored parent gives rise to only gametes bearing 'y' factor.
Gametes
Y
y
y
Yy (heterozygous ebony)
yy (homozygous yellow)
y

2. Yy
yy
Progeny obtained in the F1 generation have genotype Yy ( heterozygous ebony) and
yy(homozygous yellow).
Case 3: Cross #3
Two ebony offspring are crossed having genotype 'Yy'.
Genotype of the progeny in F2 generation can be obtained by using checkerboard-
Gametes
Y
y
Y
YY (homozygous Ebony)
Yy (heterozygous ebony)
y
Yy (heterozygous ebony)
yy (homozygous yellow)
Thus, phenotypic rato between Ebony & Yellow colored fruit fly -3:1 (Ebony: Yellow)
Genotypic ratio in F2 generation - YY: Yy : yy - 1: 2: 1
Case 4 :Cross #4
Mating is performed between Ebony colored fruit fly #3 having genotype 'Yy' and Ebony
colored fruit fly #2 having genotype 'YY'. #3 ebony colored fly gives rise to to different types
of gametes- one bearing 'Y' allele and the other bearing 'y' allele for body color character.
The genotype and the phenotype of the progeny in this case can be obtained using checkerboard.
Gametes
Y
y
Y
YY ( homozygous ebony)
Yy (heterozygous ebony)
Y
YY
Yy
Thus all the progeny obtained are Ebony in color but they differ in their genotypes.
Genotypic ratio in the progeny obtained from the cross - YY : Yy - 1 :1.
Thus, 50% of the progeny are homozygous Ebony while 50% of the progeny are heterozygous
Ebony.

3. Gametes
Y
y
y
Yy (heterozygous ebony)
yy (homozygous yellow)
y
Yy
yy
Solution
Answer:
Two Yellow colored and two ebony colored fruit flies are provided as mentioned in the question.
It is not known to us, of them, which one is the dominant trait for the body color character.
Case 1: Cross #1
Yellow colored fruit flies are crossed with ebony colored fruit flies and as a result all progeny
obtained in the F1 generation are of a single color- Ebony. This observation leads to the
impression that Ebony coloration is the dominant trait whereas Yellow is the recessive trait.
Both the parents are homozygous for the trait and are pure breeding varieties. If that would not
have been the case, in the F1 generation itself two variants- both Ebony and Yellow colored
progeny would have appeared.
According to Mendelian laws,
Let, 'Y' be the factor responsible for Ebony coloration and 'y' be the factor responsible for
Yellow coloration.
Thus, in the parental generation,
Genotype of the parent having Ebony coloration (homozygous pure breeding variety) - YY
Genotype of the parent having Yellow coloration (homozygous pure breeding variety) - yy
Hence, genotype of the progeny in F1 generation - Yy
Case 2 : Cross #2
In the present case it was observed that 113 Yellow fruit flies were obtained and 120 Ebony fruit
flies were obtained in the F1 generation as a result of a cross between an ebony & another yellow
fruit fly. So, in the F1 generation, both the variants were obtained almost approximately in 1:1
phenotypic ratio. Since both the variants were obtained, it may be concluded that parent bearing
ebony coloration was heterozygous whereas the yellow colored fly was a pure breeding variety.
Thus,

4. Genotype of the parent having Ebony coloration - Yy (heterozygous)
Genotype of the parent having Yellow coloration -yy (homozygous)
Ebony colored parent gives rise to two types of gametes- one bearing 'Y' factor and the other
bearing 'y' factor. Yellow colored parent gives rise to only gametes bearing 'y' factor.
Gametes
Y
y
y
Yy (heterozygous ebony)
yy (homozygous yellow)
y
Yy
yy
Progeny obtained in the F1 generation have genotype Yy ( heterozygous ebony) and
yy(homozygous yellow).
Case 3: Cross #3
Two ebony offspring are crossed having genotype 'Yy'.
Genotype of the progeny in F2 generation can be obtained by using checkerboard-
Gametes
Y
y
Y
YY (homozygous Ebony)
Yy (heterozygous ebony)
y
Yy (heterozygous ebony)
yy (homozygous yellow)
Thus, phenotypic rato between Ebony & Yellow colored fruit fly -3:1 (Ebony: Yellow)
Genotypic ratio in F2 generation - YY: Yy : yy - 1: 2: 1
Case 4 :Cross #4
Mating is performed between Ebony colored fruit fly #3 having genotype 'Yy' and Ebony
colored fruit fly #2 having genotype 'YY'. #3 ebony colored fly gives rise to to different types
of gametes- one bearing 'Y' allele and the other bearing 'y' allele for body color character.
The genotype and the phenotype of the progeny in this case can be obtained using checkerboard.
Gametes
Y

5. y
Y
YY ( homozygous ebony)
Yy (heterozygous ebony)
Y
YY
Yy
Thus all the progeny obtained are Ebony in color but they differ in their genotypes.
Genotypic ratio in the progeny obtained from the cross - YY : Yy - 1 :1.
Thus, 50% of the progeny are homozygous Ebony while 50% of the progeny are heterozygous
Ebony.
Gametes
Y
y
y
Yy (heterozygous ebony)
yy (homozygous yellow)
y
Yy
yy