University of Colorado, Boulder
Principles of Genetics Lab, MCDB 2151, Tuesday 4 – 5:50pm
TA: Alexander Martinez
Abstract
In this lab, we carried out two different crosses using Drosophila; a monohybrid cross and a sex-linked cross. This lab specifically tested Mendel’s laws of independent assortment and the law of segregation in genetics. We selected males and females of two different phenotypes and mated them (and their succeeding offspring) to develop a better understanding of how specific traits are inherited. After the parent generation produced enough offspring, we killed them off and waited for the F1 generation to hatch, and then did the same for the F2 generation, the resulting phenotypes…show more content… Drosophila specifically, have been used as a model organism for understanding genetic inheritance. The Drosophila fly is a great organism to use to study inheritance because of the copious number of offspring the females can produce in their short, two-week lifespan, as well as the fact that the flies are easily bred in a laboratory setting ("Yourgenome.Org"). For this particular experiment, we were to select male flies of a specific phenotype and females of a specific phenotype and predict the resulting phenotypes of the F2 generation after mating the parent generation. We hypothesized that the parents’ genotypes can be accurately determined based off of the phenotypic ratios of the F1 and F2 generations. We chose to breed male flies that had white eyes and normal wings with female flies that had red eyes and vestigial wings. Based off of our parent generation, we calculated and analyzed and chi-squared test and compared our observed numbers of each phenotypes to our expected numbers. The Drosophila species is a very beneficial organism to study because 75 percent of the genes that cause disease in humans can also be found in the Drosophila and the reproduction cycle allows for analyzation of several generations within a few…show more content… In the fourth week, the vile now had the F1 generation in it. We knocked out the flies again separated them into groups by phenotype and sex. We counted the numbers of each group and recorded the data. We then placed all the F1 flies back in the vile so that they could mate and produce our F2 generation the following week.
During the fifth week, we had to kill all the F1 flies by knocking them out and placing them in the fly morgue so that the only flies (larvae more like) in the vile are from the F2 generation.
The sixth week is when we counted the F2 generation of our flies and determined their phenotypes and sex. We counted the ratios and that is when we realized that something had gone wrong because our F2, F1, and Parent generation were all the same.
Results
Monohybrid and X-Linked Cross of Parent Flies
Since we accidentally bred males and females of the same phenotype, the parent, F1, and F2 generation’s crosses would all have the genotypes of X-YWW (white eye and normal wing males) and X-X-WW (white eye and normal wing females) and the cross between the males and females would produce the following cross:
Parents
X-W
X-W
X-W
X-W
