The basic concepts of transmission genetics is introduced using the dihybrid cross of Drosophila melanogaster to develop an understanding in genetic concepts of how genes are transmitted. The main objective of this experiment was to enhance understanding of the patterns of inheritance in fruit flies (Drosophila melanogaster). A dihybrid cross was set up using a set of F1 generation flies that eventually give rise to F2 generation. The phenotypic ratios of these flies are then analysed namely wild type, dumpy mutant, sepia, double mutant. The overall experiment explains the mechanisms of inheritance. (Summarised results and principle conclusions). The results collected conveyed…… To conclude Introduction In a period of 2-6 weeks Mendelian inheritance …show more content…
In terms of length/size it is found that females are generally larger than males. Adults and larvae feed on yeast that grows on ripened fruit and also on bacteria, but for experimental purposes, these fruit flies are fed yeast cells found in carbohydrates. Drosophilae are ideal organisms to demonstrate basic concepts of the transmission of genes, because they are capable of producing large numbers of offspring at a time and have a life cycle of ± 10 days depending on environmental conditions. Significant amount of features such as eye colour, wing shape and segment organization can be used to identify these organisms using a light microscope (Textbook pg519). Any changes in the above mentioned features result in mutations in genes. The cross conducted in this experiment was between the wild type female (dp+/dp+; se+/se+) and the dumpy sepia male (dp/dp; se/se). Using a dihybrid cross of wild type and dumpy sepia mutant it was hypothesized that the F1 generation would all be wild type and that the F2 generation is predicted to convey a 9:3:3:1 ratio with 9 out the 16 being the wild type, the one 3 out of 16 to be dumpy mutant, the other one of the 3 out of the 16 being the sepia mutant and the 1 out of the 16 being the double mutant. The main aim of this experiment was to further the understanding of how genes are transmitted using a dihybrid cross with the purpose to demonstrate …show more content…
The F1 generation was then crossed to produce the F2 generation of which was expected to have the phenotypic ratio of 9:3:3:1 of which 9 were expected to be wild type because there were no mutations, ratio of 3 were expected to be dumpy mutant with only one mutation, the other 3 was expected to be sepia mutant also with only one mutation and the ratio of 1 to be that of the double mutant. According to the chi-square test above there is a significant difference between expected frequencies and observed frequencies. The chi-squared value of individual groups of 71.6315 is greater than the critical value of 7.81 therefore the null hypothesis is rejected. The chi-squared value of all student of 51.6598 is greater than the critical value of 7.81 therefore the null hypothesis is rejected. The chi square value of all student is less than the chi-square value of individual results, which further stipulates that the samples used had a large data, furthermore a large data set makes the goodness of fit test sensitive to small values, this then results in deviation from distribution. A smaller sample should have been