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Drosophila

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Submitted By lowhit7
Words 1490
Pages 6
Loreen Whitfield
11/6/12
Section 6
Drosophila
I. Introduction
Over the course of this lab we are to familiarize ourselves with Drosophila, fruit flies, which is an important experimental organism. It is useful for genetic research because of its genome which represents eukaryotic organisms. The life cycle of the fruit fly is short which allows it to be easily observed over its lifetime. Also it can be reproduced and handled in large numbers. From this lab we can expect to learn how to etherize the flies and avoid killing them and to determine the sex of the flies. Finally we will be able to identify the differences between a normal, wild type, and a mutant fly.
Determining the sex of the flies can be done because of different characteristics between the sexes. Females tend to be larger than males, an alternating banded posterior, and an oviposterior plate. Males are usually smaller than females and have sex combs located on the forelegs.
The normal Drosophila physical characteristics can be grouped into four main features. The body consists of a yellow and gray pigmentation, eyes are brick red, and wings are in an elliptical shape with veins along them. Differentiation from this can result in a mutant fly which are more commonly found in a lab as opposed to nature. Mutant characteristics can appear in one or more different aspects of the Drosophila appearance.
The purpose for this lab is to conduct a cross between two different mutations to determine whether they are sex-linked or show autosomal dominant-recessive inheritance. The two mutations being observed are radius incompletes (RI) wing veins and white (W) eye color. The hypothesis I propose is that the mutation for white eye color is sex linked and incomplete veins are autosomal recessive. The phenotype ratio will be 9:3:3:1 and the genotype ratio will be 6:3:3:2:1:1. II. Materials and Methods
Materials for this experiment involved vials, cotton, ether, and a large number of flies containing mutants. 1. Virgin flies are obtained, meaning they have not mated yet, and are etherized. We separate the white-eyed and incomplete vein flies, which are the ones we are interested in. 2. The flies are etherized by saturating a cotton ball with ether and putting it into a vial. Once the Drosophilas are no longing moving about they are ready to work with. 3. We identify and isolate a female with radius incompletus and a white-eyed male using a dissecting microscope. 4. These flies are allowed to mate and when examined again, eight days later, we obtain 9,926 of their offspring. They are singled out in the pupae stage and allow to matured, but not allowed to mate. 5. This F1 generation is etherized, sex is determined, and we calculated the phenotype ratio. All the flies showed a wild type phenotype. 6. A F1 female and a F1 male are allowed to mate and produce 9,908 offspring. These flies are a part of the F2generation. 7. The sex and the phenotypes are observed for the F2 generation. Here we figure out the phenotype ratios. 8. The experiment is conducted again to confirm our hypothesis. In the second experiment the female has the white-eyes present, and the male holds the radius incompletus mutation.

III. Results
Female: W Male: RI TABLE 1: F1 Generation cross between Female: W and Male: RI Phenotype | Number | Proportion | Ratio | Female: + | 5027 | .5001 | 1.001 | Male: W | 5024 | .4999 | 1.000 |

TABLE 2: F2 Generation cross between Female: + and Male: W from F1 generation Phenotype | Number | Proportion | Ratio | Female: + | 1849 | .1858 | 3.041 | Male: + | 1844 | .1853 | 3.033 | Female: W | 1896 | .1905 | 3.118 | Male: W | 1826 | .1834 | 3.003 | Female: RI | 608 | .0611 | 1.000 | Male: RI | 637 | .0640 | 1.048 | Female: W,RI | 648 | .0651 | 1.066 | Male: W,RI | 646 | .0649 | 1.063 | Total: | 9954 | | |
Chi-Squared Test Statistic: 4.4424
Degrees of Freedom: 7
Level of Significance: .7276
Recommendation: Do not reject hypothesis
Female: RI Male: W I. TABLE 3: F1 Generation cross between Female: RI and Male: W

Phenotype | Number | Proportion | Ratio | Female: + | 4968 | .4967 | 1.000 | Male: + | 5034 | .5033 | 1.013 | II.
TABLE 4: F2 Generation cross between Female: + and Male: + from F1 generation Phenotype | Number | Proportion | Ratio | Female: + | 3742 | .3719 | 6.185 | Male: + | 1901 | .1889 | 3.142 | Male: W | 1890 | .1878 | 3.124 | Female: RI | 1269 | .1261 | 2.098 | Male: RI | 655 | .0651 | 1.083 | Male: W, RI | 605 | .0601 | 1.000 | Total: | 10062 | | | III. Chi-Squared Test Statistic = 2.4667 IV. Degrees of Freedom = 5 V. Level of Significance = .7815 VI. Recommendation: Do not reject your hypothesis VII.
The two crosses performed generated the appropriate results to prove my hypothesis. In the first cross a white eyes appeared in the F1 generation, causing it to be unconvincing because both are supposed to be recessive. So I executed another cross with the mutations present in the opposite sex.
In the second cross, both mutations appear to be recessive since neither is expressed in the offspring. There was no white eyed female in the F2 generation so we can assume that it is sex-linked. The cross above proves my hypothesis of a 9:3:3:1 ratio showing wild type, white eyes, incomplete veins, and white eyes and incomplete veins respectively.

IV. Discussion
Female: W Male: RI
C+C+XWXW CRICRIX+Y
Possible Gametes
C+XW CRICRIX+ CRIY
Table 5: F1 Generation Punnett Square | C+ XW | CRI X+ | CRI C+ XW X+Female: + | CRIY | CRI C+ XW YMale: W |

Female (F1): + Male (F1): W
CRI C+ XW X+ CRI C+ XW Y
Possible Gametes
CRIXW CRIXW
C+XW C+XW
C+X+ CRIY
CRIX+ C+Y
Table 6: F2 Generation Punnett Square

| CRIXW | C+XW | C+X+ | CRI X+ | CRI XW | CRI CRIXWXWFemale: RI, W | CRI C+ XWXWFemale: W | CRI C+ XW X+Female: + | CRICRIXW X+Female: RI | C+XW | CRI C+XWXWFemale: W | C+C+ XWXWFemale: W | C+ C+ XWX+Female: + | CRIC+XRIYFemale: + | CRIY | CRICRI XWYMale: RI, W | C+CRI XWYMale: W | CRIC+X+YMale: + | C+ C+ X+ X+Male: RI | C+Y | CRIC+XWYMale: W | C+C+ XWYMale: W | C+ C+ X+YMale: + | CRIC+X+YMale: + |

Female: RI Male: W I. CRICRIX+X+ C+C+XWY II. Possible Gametes: III. CRIX+ C+XW C+Y IV. Table 7: F1 Generation Punnett Square

| CRI X+ | C+ XW | CRI C+ X+ XWFemale: + | C+Y | CRI C+ X+YMale: + |

Female (F1): + Male (F1): + V. CRIC+XWX+ CRIC+X+Y

VI. POSSIBLE GAMETES VII. CRIXW CRIX+ VIII. CRIX+ CRIY IX. C+XW C+X+ X. C+X+ C+Y XI. XII. Table 8: F2 Generation Punnett Square XIII. | CRI XW | CRI X+ | C+ XW | C+ X+ | CRIY | CRICRIXW YMale: RI, W | CRICRIX+ YMale: RI | CRI C+ XW YMale: W | CRI C+ X+YMale: + | C+ X+ | CRI C+ XW X+Female: + | CRI C+ X+ X+Female: + | C+ C+ XW X+Female: + | C+ C+ X+ X+Female: + | C+Y | CRI C+ XW YMale: W | CRI C+ X+ YMale: + | C+ C+ XW YMale: W | C+ C+ X+YMale: + | CRI X+ | CRICRIXW X+Female: RI | CRICRIX+ X+Female: RI | CRI C+ XW X+Female: + | CRI C+ X+ X+Female: + |

My hypothesis stated that radius incompletus is autosomal recessive and the mutation for white eyes was sex linked. The punnett squares, Table 7 and 8, are what I used to prove my hypothesis to be valid. Neither of the mutations is dominant because they are not present in the first set of off springs, and prove to be recessive considering the parents have the genes but are still wild type. Since there were no white eyed females it can be conclude that they need to be present on both X chromosomes. The mutation for whites eyes appeared in the males because they only need to receive one of the mutated X’s to show the trait. It can be deducted that the mutation for incomplete veins is autosomal recessive considering it only shows up when both chromosomes have the defect. This is shows a typical 9:3:3:1 phenotype ratio. V. Summary
This purpose of this lab was to show inheritance when two different mutations are used to test sex linked dominant or recessive characteristics. A female with radius incompletus and one male with white eyes mated to produce a F1 generation, which we used to attain an F2 generation. Both genes appeared to be recessive because they did not appear in the first pair of off springs: all wild type. The fact that white eyes is sex-linked was concluded considering they were no female with white eyes, indicating the need for two X chromosomes with the mutation. Through the use of punnett squares we were able to find the inheritance. I. II. VI. References
Biology Department Faculty. Principles of Cell and Molecular Biology Laboratory Exercises. United States: Pearson Custom Publishing. 2004 ed. Print…...

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