AbstractionThis lab involved a monohybrid mutual cross and a sex-linked cross using Drosophila melanogaster fruit flies. After arousing the flies. puting them in media. and allowing them cross strain. we analyzed and recorded the phenotypes that were observed. The P1 flies were anesthetized so sexed by detecting their phenotypes and every bit distributed into the media we made for their sexual intercourse. When a sufficient sum of offspring was present in the civilization bottle the P1 coevals was killed.
After the offspring developed in the F1generation of the sex-linked cross the phenotypes were observed and recorded. After the F1 coevals of the monohybrid cross developed the procedure was repeated to make an F2 coevals and the consequences were ascertained and recorded. Class information was besides included in the consequences for comparings. We found that though some of the consequences for each of the crosses were close to the void hypothesis. they did non accept the chance of the Chi-Square analysis. This means that even though there are outlooks for the consequences. what happens in nature can about ne’er be controlled wholly.
Background
The first experiments using the fruit fly Drosophila melanogaster were performed by Thomas Morgan. when in 1910 he spotted a white-eyed fruit fly in his fly room. However the first reported “mutants” found among the fruit fly were observed in 1907 by Frank Lutz of the Carnegie Institution. He reported different wing forms and. by 1908. had noticed the proliferation of midget mutations. By the 1980s these finds have spawned into its ain field of survey by geneticists sometimes referred to as “Drosophilists” . ( Taubes 2012 )
The intent of our D. melanogaster Monohybrid Cross experiment was to analyze the familial traits based on Mendelian heritage. In this cross. the wild type ( red-eyed ) phenotype is 100 % dominant over the recessionary sepia-eyed trait. The void hypothesis for the F1 coevals is 100 % wild-type and the F2 coevals has a void hypothesis of 75 % red-eyed and 25 % sepia-eyed. ( lab manual ) .
The intent of our D. melanogaster Sex-Linked Inheritance experiment was to detect that non all traits are acquired autosomally. Through this lab we were able to see that X-linked traits are inherited in predictable forms because of their dependance on the sex chromosome. The consequence of the crosses depends on which parent carries the phenotype wished to be observed before the existent cross. Since we crossed white-eyed females with red-eyed males the void hypothesis for this experiment was expected to be a 1:1 ratio of white-eyed males to red-eyed females ( lab manual ) . Because males merely carry one X chromosome ( inherited from their female parent which besides determines oculus colour ) they are ever hemizygous for the sex chormosomes. ( N. D. 2009 ) .
Experimental Set-up:Monohybrid Cross:On August 28. 2012 a civilization bottle with Drosophila media and barm was prepared and labeled. Six red-eyed fruit flies ( genotype RR ) of one sex and six sepia-eyed fruit flies ( genotype rr ) of the other sex were transferred into the civilization bottle after being anesthetized. After a period of approximately seven to ten yearss legion larvae and some pupae became seeable inside the bottle. To forestall any intergenerational coupling. the P1 coevals ( original grownup parent flies ) were removed from the bottle go forthing merely the progeny to emerge into the F1 coevals.
The F1 coevals was evident inside the civilization bottle after another seven to ten twenty-four hours period. Using FlyNap these fruit flies were put under anaesthesia for observation. The phenotype of the F1 coevals fruit flies was observed to be all red-eyed ; therefore the genotype was noted to be Rr.
On September 11. 2012 a new civilization bottle with fresh media and barm was prepared and labeled. Six male flies and six female flies from the F1 coevals were added to the new civilization bottle. Once larvae and pupae became seeable the grownup F1 coevals fruit flies were removed from the civilization go forthing behind the F2 coevals offspring. Seven to ten yearss subsequently the progeny had developed into grownup flies. The F2 coevals was anesthetized and so separated and counted based on oculus phenotype which was either ruddy or reddish brown.
The Numberss observed were used to cipher a Chi-Square statistical analysis which was used to find whether or non the void hypothesis of a 3:1 ratio for the F2 coevals was accepted. This information was combined with informations from the full category to increase the sample population and to cipher another Chi-Square.
Sex-linked Cross:A civilization bottle with Drosophila media and barm was prepared and labeled. Six D. melanogaster wild-type male flies and six white-eyed female flies were transferred into the bottle. Seven to ten yearss subsequently legion larvae and some pupae became seeable inside the bottle. At this clip the P1 coevals flies were removed from the bottle go forthing merely the F1 coevals offspring as to avoid intergenerational coupling.
Adult flies of the F1 coevals were seeable after a hebdomad. These grownup flies were anesthetized and the phenotypes ( sex and oculus colour ) were observed and recorded. A Chi-Square statistical analysis was calculated to find if the void hypothesis of 1:1 for fly sex and oculus colour would be accepted or rejected. This information was combined with informations from the full category to increase the sample population and a 2nd Chi-Square was calculated.
ConsequencesThe P1 Generation for the monohybrid cross consisted of six homozygous red-eye ( RR ) fruit flies of one sex and six homozygous reddish brown ( rr ) fruit flies of the other sex. As shown in Table 1 the F1 coupling consisted of being all heterozygous for the wild-type red-eye ( Rr ) in colour. The F2 coevals is besides presented demoing an unexpected ratio and the Chi-square is calculated in Table 2. The P1 coevals of the sex-linked heritage started with white-eyed females and red-eyed males and the consequences in the F1 offspring are presented in Table 3 while the Chi-square is illustrated in Table 4.
Monohybrid Cross:The entire ascertained Numberss counted was 358 with 333 ( 93 % ) of them holding the red-eye phenotype and a genotype ( s ) of homozygous RR and/or heterozygous Rr. The staying 25 ( 7 % ) were of the sepia-eye coloured phenotype with a definite genotype of homozygous rr. The expected ratio of the void hypothesis was 3:1 ( 75 % ) red-eye colored and 1:3 ( 25 % ) sepia-eye colored or expected Numberss of 268. 5 ( ruddy ) and 89. 5 ( reddish brown ) . P1 Eye Genotype & A ;The Chi-Square computations were figured by taking the standard Chi-Square calculations as shown in Table 2. The Chi-Square figure for our experiment was 62. 0. This figure was important in comparing to what would hold been needed for the void hypothesis to hold been accepted. therefore enabling the decision of a jilted hypothesis. The category as a whole besides calculated the Chi-Square by adding up all the ascertained Numberss and expected Numberss to organize a category sum. This figure was significantly larger at a Chi-Square of 206. 7. besides taking to a rejected void hypothesis.
Sex-linked Cross:The P1 genotype and phenotypes consisted of: XwXw white-eyed females and XwY Red-eye males. Six of each was crossed and the F1 coevals was shown to hold consisted of: Xw+Xw red-eye females and XwY white-eye males. The expected ratio was 1:1 ruddy to white. With a entire count of 357 fruit flies. the ascertained figure of red-eye females was 220 while the ascertained figure of white-eye males was 137 which did non suit the expected ratio.
The Chi-Square for our group was found to be 19. 3 which was excessively high to be accepted. therefore the void hypothesis was found to be rejected. The Chi-Square of the category was found to be 50. 0 and one time once more excessively high to be accepted. therefore the void hypothesis was rejected.
DecisionThe consequences of both of these experiments were similar in footings of the credence or rejecting of the void hypothesis. The expected chance ratios were theoretically supposed to hold closely mimicked the experimental consequences ; nevertheless chance is merely that. likely. There is no warrant. due to randomness of the system. that there will be a ratio that will of all time precisely mimic existent life scenarios in nature.
In both experiments the Chi-Square figure showed that both void hypotheses were rejected. These Numberss were non comparably near to those needed to hold had an accepted void hypothesis. The birthrate of these fruit flies. the frequence of coupling. the cistrons that were involved with crossing over. and the chromosomes that were passed on to the following coevals ( s ) were all due to random mixture and therefore it could merely be merely a possibility that certain traits pass on to the following coevalss. Mutants can besides act upon such ratios with traits that were non accounted for in the yesteryear and are accordingly passed on to future coevalss. ( such as albinism ) .
Mentions
Geneticss Lab Manual. ( 2012 ) .N. D. ( 2009 ) . Sex-linked Inheritance: Drosophila. National Health Museum. Retrieved October 5. 2012 from: hypertext transfer protocol: //www. accessexcellence. org/RC/VL/GG/sex. php.Taubes. G. A. ( 2012 ) . The “Fly People” Make History. The Genes We Share. Retrieved from hypertext transfer protocol: //www. hhmi. org/genesweshare/b100. hypertext markup language.
