Data set A summarizes F2 numbers from a cross between two, true breeding Drosoph
ID: 63031 • Letter: D
Question
Data set A summarizes F2 numbers from a cross between two, true breedingDrosophila strains (P generation), which differ with respect to two traits. The gene alleles can be dominant or recessive, and autosomal or X-linked.
DATA SETS A:
A2
wild type, females 564
black body, males 294
wild type, males 292
orange eyes, females 182
orange eyes, black body,
males 91 orange eyes, males 98
For this part of the report do the following:
Assign genetic symbols to the genes and alleles involved. It does not matter what they are as long as you have a clear legend. For example if you suspect an X-linked trait, make it X^r+ or X^r.
Produce one genetic hypothesis about the mode of inheritance for both the genes from your data set. For example, the allele for yellow eyes is X-linked and recessive and the allele for long legs is autosomal dominant.
Illustrate your genetic hypothesis from above. For example, you could use a breeding diagram (flow chart), in which the P, F1, and F2 generations and their genotypes andphenotypes are clearly indicated. Include the expected phenotypic ratios in the P, F1, and F2generations. There is no single hypothesis to be tested but your hypothesis must be plausible based on your data.
Analyze whether the data fits your hypothesis by the applying the Chi-square test. If you believe one or both genes are sex-linked, then show your analysis of males and females separately
Explanation / Answer
From the given information, It can be interpreted that body color is an X-linked trait and eye color is autosomal trait.
Female genotype
Male genotype
Parent genotype
XB XB C C
Xb Y c c
F1 generation
XB Xb C c
XB Y C c
XB = X-linked dominant allele for body color
Xb = X - linked recessive allele for body color
C = Dominant allele for eye color
c = recessive allele for eye color
The following are the genotypes of the F2 generation, if the cross is done between the male and female of F1 generation:
Female Gametes
Male gametes
XB C
XB c
Y C
Y c
XB C
XB XB C C
Wild type(F)
XB XB C c
Wild type (F)
XB Y C C
Wild type
XB Y C c
Wild type
XB c
XB XB C c
Wild type (F)
XB XB c c
orange eye(F)
XB Y c C
Wild type
XB Y c c
Orange eyes
Xb C
Xb XB C C
Wild type (F)
Xb XB C c
Wild type (F)
Xb Y C C
Black body
Xb Y C c
Black body
Xb c
Xb XB C c
Wild type (F)
Xb XB c c
Orange eyes (F)
Xb Y c C
Black body
Xb Y c c
Black body, orange eyes
From the above table, the following shall be the genotype proportions:
Expected results
Observed result
Wild type females
43%
37%
Black body males
19
19.3
Wild type males
19
19.2
Orange eyes females
12.5
12.0
Orange eyes, black body males
6.25
6.0
Orange eyes males
6.25
6.5
* The alleles for body color are X linked and alleles for eye color are autosomal. Wild type is a dominant inheritance, black body and orange eye color are homozygous recessive (or recessive) traits.
Female genotype
Male genotype
Parent genotype
XB XB C C
Xb Y c c
F1 generation
XB Xb C c
XB Y C c
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