Design and perform a cross between a female fly with vestigial wing size and a male fly with an...

Question

Design and perform a cross between a female fly with vestigial wing size and a male fly with an incomplete wing vein mutation. Carefully study the phenotype of this male fly to be sure that you understand the effect of the incomplete allele.What did you observe in the F₁
generation?
Note: It may be helpful to click up and down in this display box to closely compare the phenotypes of the F₁
and P generations.

Was this what you expected? Why or why not? Once you have produced an F₁
generation, mate F₁
flies to generate an F₂
generation.

Study the results of your F₂
generation and then answer the following questions.

Which mutation is epistatic? Is the vestigial mutation dominant or recessive? Determine the phenotypic ratio that appeared in the dihybrid F₂
generation, and use chi-square analysis to accept or reject this ratio.

Perform another experiment by mating a female fly with the apterous wing size mutation with a male fly with the radius incomplete vein structure mutation. Follow this cross to the F₂
generation.

Which mutation is epistatic? Is the apterous wing mutation dominant or recessive?

Assignment #2:
Recombination

Mendel's law of independent assortment applies to unlinked alleles, but
linked genes--genes on the same chromosome -- do not assort independently. Yet linked genes are not always inherited together because of
crossing over. Crossing over, or
homologous recombination, occurs during prophase of meiosis I when segments of DNA are exchanged between homologous chromosomes. Homologous recombination can produce new and different combinations of alleles in offspring. Offspring with different combinations of phenotypes compared with their parents are called
recombinants. The frequency of appearance of recombinants in offspring is known as recombination frequency. Recombination frequency represents the frequency of a crossing--over event between the loci for linked alleles. If two alleles for two different traits are located at different positions on the same chromosome (heterozygous loci) and these alleles are far apart on the chromosome

005_jk-aqdbaax2.doc

Robert · Accepted Answer

1. Design and perform a cross between a female fly with vestigial wing size and a male fly with 
an incomplete wing vein mutation. Carefully study the phenotype of this male fly to be sure 
that you understand the effect of the incomplete allele.
Allele for vestigial wing Vg which is recessive for normal wing Vg+ 
Allele for incomplete vein is RI which is recessive for normal vein RI 
Thus genotype of female is VgVg RI+RI+ 
Genotype of male is Vg+Vg+RIRI
    Cross can be represented as
    VgVg RI+RI+ X  Vg+Vg+RIRI
   F1 progeny: Vg+VgRI+RI: All wild type
    Cross between F1 offspring 
   Vg+VgRI+RI   X   Vg+VgRI+RI
  Result can be represented in punnet square:
gametes female Vg+RI+        Vg RI+         Vg+RI          VgRI 
male 
Vg+RI+ Vg+ Vg+RI+RI+ 
Wild type  
Vg+ VgRI+RI+ 
Wild type 
Vg+ Vg+RI+RI
Wild type 
Vg+ VgRI+RI
Wild type
VgRI+ Vg+ VgRI+RI+ 
Wild type 
Vg VgRI+RI+ 
Vestigial  
Vg+ VgRI+RI 
Wild type 
Vg VgRI+RI 
vestigial
Vg+RI Vg+ Vg+RI+RI 
Wild type 
Vg+ VgRI+RI 
Wild type 
Vg+ Vg+RIRI 
Incomplete vein 
Vg+ VgRIRI 
Incomplete vein
VgRI Vg+ VgRI+RI 
Wild type 
VgVgRI+RI 
vestigial 
Vg+ VgRIRI 
Incomplete vein 
Vg VgRIRI 
Incomplete vein
Phenotypic frequency: 9 wild type: 3 vestigial: 4 incomplete vein fly.
Thus in F1 generations all offsprings are wilds type. This is expected because according to 
Mendelian theory dominant allele would express over the recessive. This is the case here.
In F2 generation result shows that phenotypic ratio of offspring is 9 wild type: 3 vestigial: 4 
incomplete vein fly. 
This result does not follow the Mendel’s rule, because for dihybrid cross phenotypic ration of F2 
is 9:3:3:1
Here this phenotypic ration indicates the presence of recessive epistasis. Because offsprings with 
homozygous allele for incomplete vein (RI) are recessive and their phenotype is incomplete vein. 
Thus, incomplete vein gene (RI) is recessive epistatic over vestigial wing gene ( Vg). And 
vestigial wing gene (Vg) is hypostatic gene.
2. Perform another experiment by mating a female fly with the apterous wing size mutation 
with a male fly with the radius incomplete vein structure mutation. Follow this cross to 
the F2 generation.  
Which mutation is epistatic? Is the apterous wing mutation dominant or recessive?
Allele for apterous wing size mutation is Ap 
Allele for radius incomplete vein structure mutation is RI
Genotype of female would be ApApRI+RI+   
Genotype of male would be Ap+Ap+RIRI
Cross can be represented as  
ApApRI+RI+   X  AP+Ap+RIRI
F1: AP+ApRI+RI = all wild type.
F2:  Ap+ApRI+RI  X  : Ap+ApRI+RI
This can be presented in punnet square:
gametes female Ap+RI+        ApRI+         AP+RI          ApRI 
male 
Ap+RI+ Ap+ Ap+RI+RI+ 
Wild type  
Ap+ ApRI+RI+ 
Wild type 
Ap+ Ap+RI+RI
Wild type 
Ap+ ApRI+RI
Wild type
ApRI+ Ap+ ApRI+RI+ 
Wild type 
ApApRI+RI+ 
Apterous
  Ap+ApRI+RI 
Wild type 
Ap ApRI+RI 
Apterous
Ap+RI Ap+ Ap+RI+RI 
Wild type 
Ap+ ApRI+RI 
Wild type 
Ap+ Ap+RIRI 
Incomplete vein 
Ap+ ApRIRI 
Incomplete vein
ApRI Ap+ ApRI+RI 
Wild type 
ApApRI+RI 
Apterous
Ap+ ApRIRI 
Incomplete vein 
ApApRIRI 
Incomplete vein
Phenotypic frequency: 9 wild type : 3 vestigial : 4 incomplete vein fly.
In F2 generation result shows that phenotypic ratio of offspring is  9 wild type : 3 apterous : 4 
incomplete vein fly. 
This result does not follow the Mendel’s rule, because for dihybrid cross phenotypic ration of F2 
is 9:3:3:1
Here this phenotypic ration indicates the presence of recessive epistasis. Because offsprings with 
homozygous allele for incomplete vein (RI) are recessive and their phenotype is incomplete vein. 
Thus, incomplete vein gene (RI) is recessive epistatic over apterous wing gene( Vg).
Apterous wing is recessive wing.
Assignment  #2:  
1. To understand how recombination frequencies can be used to determine an approximate 
map distance between closely linked genes,

Sun	Mon	Tue	Wed	Thu	Fri	Sat
30	31	1	2	3	4	5
6	7	8	9	10	11	12
13	14	15	16	17	18	19
20	21	22	23	24	25	26
27	28	29	30	1	2	3

Design and perform a cross between a female fly with vestigial wing size and a male fly with an incomplete wing vein mutation. Carefully study the phenotype of this male fly to be sure that you...

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