Art history analysis paper

Monohybrid cross of wild type and wingless Drosophila melanogaster

Abstract

The principles of classical genetics are used to predict how genes determine basic patterns of inheritance, and are frequently explored using the common fruit fly, Drosophila melanogaster. Not only does such research provide basic information about inheritance, it can be appliced to human inheritance. In this study, pure bred cultures of wild type dominant flies were crossed with pure bred mutant apterous flies, producing both F1 and F2 generations. While the F1 generation was all of the wild type, the F2 generation produced a ratio of 3 wild type flies to 1 apterous type lies. This ratio supports Mendel's laws of inheritance. Using such research reinforces the value of understanding these principles, and also opens the need for future research regarding the conservation of genes in the human genome, which has a practical application in the study of human genetic diseases.

Introduction

Gregor Mendel, who is referred to as the father of genetics, used evidence he gathered through selective breeding of pea plants to establish the basic laws of genetics in the mid 1800's. These laws form the basis of classical genetics because they predict how genes behave using basic patterns of inheritance. Mendel developed these laws before genes had even been identified or understood, but the principles still hold true today. They are often studied in classical genetics experiments, such as is used with the common fruit fly, Drosophila melanogaster. This model organism is used because it is easily cultured, produces a new generation within two weeks, produces up to 500 eggs in ten days, is small enough to be studied in situations with limited space, but is individually large enough for easy phenotype determination (Flagg, 2005). Because the fly has been studied for over 100 years, many genes of D. melanogaster have been identified. This identification is useful because many biological properties are similar in mammals and D. melanogaster, and about 75% of the genes that cause diseases in humans are similar to functional genes in the fly (Pandey & Nichols, 2011). Furthermore, the sequencing of the D. melanogaster genome, which was first published in 2000, provided many contributions to genome research and genome projects(Ashburner & Bergman, 2005). In this experiment, D. melanogaster strains are crossed to study the basic laws of inheritance of the flies using the wild type and wingless, or apterous, strains. The experiment is designed to understand the basic principles of a monohybird cross, to learn how to cultivate D. melanogaster, and to explain how autosomal dominant and recessive genes are inherited, including how the alleles determine the phenotypic appearance of the flies. If the wingless phenotype of D. melanogaster is inherited according to Mendel's laws for a simple dominant/recessive autosomal gene, then the phenotypes of the F2 generation should produce a Mendelian ratio of 3 wild: 1 wingless.

Methods

Materials used in the experiment included culture vessels and plugs, Drosophila culture medium, stock cultures of of homozugous wild type D. melanogaster (+/+) and homozygous apterous D. melanogaster (ap/ap) flies, markers, anesthetic, brushes, and a magnifying lens. Using culture vessels and Drosophila culture medium, each stock culture was self crossed using five flies per sex in each of the two self-crossed cultures. This cross produced two culture tubes of parent (P) generation wild type and two culture tubes of P generation apterous flies. After removing any adult flies,virgin females were obtained for each cross by selecting them within 15 hours of emerging from the pupae. The P generations were then crossed using five male +/+ and five female ap/ap in each of two cultures, and also five female +/+ and five male ap/ap in each of two cultures. This yielded the first filial ( F1) generation. The flies were anesthetized, and the phenotypes of all flies of the F1 generation were noted. Next, virgin females were obtained for each F1 cross as in the previously described procedure. The F1 flies were crossed by mating five males and five females from each of the two cultures. The data from both pairs was combined and tested for the 3:1 phoentype ratio, using chi-square distribution statistics to see if the observed data matched the expected Mendelian ratios for autosomal inheritance.