Lab Report

LabReportFlyGenetics Project A: Flies CrossNameInstitutionDateFly Genetics

Abstract:

Fruityfly scientifically known as Drosophilamelanogaster, isa small fly that lives around and feeds on fruits that have spoiled.Fruity fly is among the most used organism in biology genetics tostudy the traits since they are small, practical to work with andhave a short life cycle of approximately two weeks. This experimentaimed at identifying the genetic traits of flies. The F1 and F2generations were obtained through performance of parental crosses inorder to determine the mode of inheritance for the genetic traits.Mode of inheritance was observed to vary for all the crosses thoughthey all correlate with Mendel’s principles.

Introduction:

Drosophilamelanogaster isamong the most critical tools used in the study of genetics. Thisexperiment was carried out to determine inheritance pattern in singletrait using monohybrid cross between mutant and wild-type stocks.Fruity flies have short life span and their mode of inheritance amongthe traits can be figured out easily.

TheProject A took seven weeks. The first week entailed meeting theflies. This involved identifying the wild-type and mutant stockvials. In the second week, the mitosis and meiosis were carried out.This process involved observing mitosis in root tips of live garlic,modeling meiosis and mitosis, and removing the parents from thee flystocks. The third week involved clearing the fly vials, planning anddiscussion of project A and setting up the F1 cross for the projectA. The fourth week involved removal of parents from the Project Across. The fifth week entailed counting the F1 and setting up F2cross for Project A. Week six involved removing F2 cross and scoringthe additional F1 offspring for Project A. Finally, the seventh weekscoring the F2 offspring for project A and doing the lab report.

Inthis experiment, the choice of fruit flies was based on the fact thatthey are easy to use on FlyNap. The understanding and ideas of thisexperiment were based on experimental fly genetic principles byMendel. In simple terms, the main idea for this experiment was thedetermination of the transmission of characteristics from parents tooffspring. During the experiment, the mutations and wild-type flieswere used. The flies were napped by first separating wild-type andmutant types, after that, males and females were segregated. Thenclearing and crossing was done to determine the phenotype andgenotype. For fruity fly, the genetic make-up is genotype but theappearance is phenotype.

Hypothesis:Themutation will be autosomal and recessive, and sex-linked withdominant and recessive.

Materialsand Methods:Thematerials used included fruit flies, microscope, FlyNap, put fliesbottles, two cards, and a tape. The characteristic of flies betweenthe mutant and wild-type fly stock was identified. The identifiedflies were transferred into the new bottle vial. The male and femalefor the mutant and wild-type flies were distinguished from each otherthrough observation through a microscope. The flies were put backinto the vials after observation and food were added to the vials.

PreparingVials for the Media

Steriletransparent glass vial was obtained, and one cup of InstantDrosophilaMediumFormula 4-24 was put into the glass vial. One cup of distilled waterwas added into the vial containing the medium. A cotton plug wasplaced at the opening of the vial, and the media was allowed toabsorb for 5 minutes before the addition of flies.

Anesthetizingthe Fruit Flies

Asterile transparent glass was obtained together with a container forthe miniature Drosophilamelanogasterprovided by the B. Thornton, University of San Francisco. The fileswere transported from the Drosophilamelanogastercontainer to the empty glass vial using the FlyNap. An anestheticwand was inserted into the FlyNap solution then dipped into the glassvial that was used to obtain the flies. The anesthetic wand wasinserted into the vial for 15 seconds and about one minute, the flieshad stopped moving.

MakingSubcultures and Separating Mutant from Wild-type

Theflies, by then unconscious, were placed on an index card that wasplain colored and a dissecting microscope used to view the fliesusing a magnification of 100um. This enabled the differentiation ofmales and females. These were placed into the glass vial containingthe media and labeled using the scotch tape. The mutant flies wereseparated from the wild-type and put in vials.

SexingFruit Flies in the Pupa Case

TheProject A vials were cleared to in order to be used for collectingthe virgin male and female flies. These virgin flies were collected 8hours later after clearing the vials. Thereafter, the mutant femaleswere crossed with the wild-type males and mutant males were crossedwith wild-type females.

MakingParental Crosses to Obtain F1 Offspring

Anew culture was prepared use the same steps as outline above. Thenfive female wild-type flies were selected and added into the vialcontaining the media. Then five male mutant type were added andobserved for any mating activity.

MakingF1 x F1 crosses to Obtain F2 Offspring

Anew culture vial with the media was prepared following the abovesteps. By this time, the female wild-type and male mutant had alreadymated, and pupa collected at the sides of the glass vial. The maleand female adult flies were sexed from the F1 culture. Thereafter,five males and five virgin females from F1 generation were added intothe media in the vial.

Results

Wild-typefemale x Mutant Male F1 Generation

Table1.1 shows the parental cross between wild-type female and mutantmale. A ratio of 1:1 was expected since wild type is dominant overmutant. The trait is therefore sex-linked and not autosomalrecessive. This has no effect on the variation in number of thegenders observed.

Wild-typefemale x Mutant Male F2 Generation

Table1.2 above demonstrates F2 generation of the F1 cross betweenwild-type females with mutant males. This cross-generation has a1:2:1 ratio, confirmed by explanation of First Law of Segregation byMendel. This was expected after obtaining the first F1 results sincemutant was not observed in F1 and hence predicted to show once in F2because it was identified to be of the recessive nature.

WildType Male x Mutant Female F1 Generation

Table1.3 illustrates parental cross between wild-type males and mutantfemales. In this case, the wild-type was dominant over mutant allele.As a result, no any mutant was perceived in F1 generation.

Wild-typeMale x mutant female F2 generation

Table1.4 shows the cross between F1 generations. This presents a Mendelianratio of 3:1. This mutation is autosomal recessive and is notsex-linked like the mutant mutation. Due to its recessive nature,then it will tend to emerge in later stages apart from F1. Thedevelopment of correct ration 3:1 is especially enhanced due to thesmall sample size meaning that the error is reduced.

Wild-typefemale x Mutant male F1 generation

Table1.5 shows the parental cross between wild-type females and mutantmales. Since the wild-type is dominant over mutant allele, then themutant mutation did not occur in F1 generation

Wild-typefemale x Mutant male F2 generation

Table1.6 shows the cross between F1 generation for wild-type females andmutant males. This presents a Mendelian ratio of 3:1 since thismutation is autosomal recessive and not sex-linked. Due to therecessive nature, it means that the mutant will emerge in the latergeneration but not in F1 hence the null hypothesis is acceptable.

Discussion

Theexperiment was successful, and the hypothesis for the study wasfulfilled. The cross between wild-type female and mutant male wassex-linked and not autosomal recessive for F1. The parental crossbetween wild-type female and mutant male gave a ratio of 1:1 sincethe wild type fruit fly was dominant over mutant. The trait wassex-linked and not autosomal recessive. This had no effect on thevariation in number of the genders observed. The cross betweenwild-type female and mutant male F2 generation had a ratio of 1:2:1ratio. This was confirmed by explanation of First Law of Segregationby Mendel. This was predicted since the mutant was not available inF1 results, hence expected in subsequent crosses. This was predictedto be recessive. The parental cross between wild-type males andmutant females had no any mutant in F1 generation as wild-type wasdominant. The cross between F1 generations had a Mendelian ratio of3:1. This mutation was autosomal recessive and not sex-linked likethe mutant mutation. Due to its recessive nature, then it had toemerge in later stages apart from F1. The parental cross betweenwild-type females and mutant males did not have any mutant in F1generation since wild-type was dominant over mutant allele. However,in F2 generation, the Mendelian ratio of wild-type to mutant was 3:1,and since this mutation was autosomal recessive and not sex-linked,the mutant emerged in the later generation but not in F1 hence thenull hypothesis was fulfilled.

However,despite some challenges of some of the parents dying, especiallyafter anesthesia, the experiment progressed on well. This isreflected from the data obtained. For instance, the cross betweenwild-type and mutant was 100% correct and free of errors. Theobserved data matched with the predicted results. This experimentalwas information, particularly in areas of fly genetics. Also, theexperience obtained in this experiment has instilled a sense oforganization, hard work, and determination. These qualities arecritical both at education level, career life, and real lifesituations.

Tables

Table1.1Wild-type female x mutant male F1 generation

XB Y

XB Xb

Xb Y

XB Xb

Xb Y

Xb

Xb

Table1.2:Wild-type female x mutant male F2 generation

Xb Y

XB Xb

XB Y

Xb Xb

Xb Y

XB

Xb

XBXband XbXb=2 Wild-type females

XBY= Mutant Male

XbY = Wild-type male

Table1.3Wild Type Male x Mutant Female F1 Generation

BB

Bb

Bb

Bb

Bb

b

b

Bb=Wild-type Drosophila

Table1.4Wild-type Male x mutant female F2 generation

Bb

BB

Bb

Bb

bb

B

b

BBand Bb = 3 Wild-type Drosophila

bb= Mutant Drosophila

Table1.5:Wild-type female x Mutant male F1 generation

bb

Bb

Bb

Bb

Bb

B

B

Bb=Wild-type Drosophila

Table1.6:Wild-type female x mutant male F2 generation

Bb

BB

Bb

Bb

bb

B

b

BBand Bb = 3 Wild-type Drosophila

bb= Mutant Drosophila