Fruit Fly Research Paper

Drosophila melanogaster is a fruit fly, about 3mm in length, and it is the insect that flies around spoiled fruit. A model organism has these traits: short life cycles and rapid development, small average size, big population, and fast reproduction (NCBI). Drosophila melanogaster meet all of the criteria for being a model organism. Also, fruit flies were used because they are very easy to handle and they require minimal resources to survive, as opposed to other organisms that might need more food or more space for survival, and the life cycle for a fruit fly is about 2 weeks, and they share about 60% of DNA with Homo sapiens (NASA). In addition, there are many variations of Drosophila melanogaster such as genotypes and phenotypes. The main
way to distinct between male and female fruit flies is that male fruit flies have a dark tipped abdomen, sex combs to grab on to a female for mating. Females are relatively larger than the males, striped throughout, do not have sex combs, and the shape of the tip of the abdomen is more pointy and striped.
Furthermore, the first person to use fruit flies is Thomas Hunt Morgan, and he found the first "mutant" fruit fly in his lab in 1910.
The phenotype of the mutant fruit fly was white eyes, and this discovery, sparked an entire field of study based around these little flies. The flies can have white, red, or sepia colored eyes, the bodies can be ebony or grey, and the wings can be long, short, or wingless. Also, some mutations may be beneficial for an organism, while others may be fatal. The possible mutations for fruit flies are white (w) - white eyes, ebony (e) - dark colored body, dumpy (dp) - short wings, bar (B) - red triangle shaped eyes, vestigial (vg) - small wings, apterous (ap) - no wings, and sepia (se) - dark round eyes. Also, a “normal” Drosophila melanogaster is called a wild type and the traits for this type are large and round eyes, wings are longer than the body, and the body is mostly buff and tan colored except the
banding.
To expand, Thomas Hunt Morgan started his career when genetics was not defined as a career/field of study.
He was interested in experiments and he wanted the answers to his questions about life such as: what are inherited factors, where are they located, and how are inherited factors passed on to the next generation? Morgan attempted to answer his questions by using Drosophila melanogaster, or fruit fly, because it can be bred cheaply and reproduces quickly. After multiple examinations and tests, Morgan and his colleagues discovered the Chromosomal Theory of Inheritance. In addition, for genetic crosses of fruit flies, there are three types of inheritance patterns that are relevant in this lab. The first is monohybrid - one single trait is involved, the second is dihybrid - two different traits are involved, and sex-linked - the pattern of inheritance that results from a mutant gene located on either the X or Y chromosome. Also, in relation to genetic crosses, it is necessary for the females in the parental generation to be virgins because this assures that all breeding/genetic crosses that are done are indeed from the parents of the most recent generation. If not, then an offspring can be inadvertently seen as a parent during
experimentation. Next, fruit flies have a life cycle that consists of four stages: egg, larva, pupa, and adult. There are numerous factors that can affect the length of the life cycle for fruit flies such as temperature which at room temperature. The eggs are small, oval-shaped, and 0.5mm long and they have a pair of filaments at one end that holds them from sinking into the food, which is usually where the eggs are laid. Larvae are maggots that are small and they spend most of their time eating food. In addition, Drosophila melanogaster larvae pass through the culture medium where they eat, and finally reach a size of up to 4.5 mm in length; the salivary glands contain large chromosomes that can be seen through a microscope (NCBI). After, the pupal stage begins and the larva becomes a pupa and it slowly climbs up the side of the tube. At first the adult is pale in color, the wings are crumpled, and its sex is difficult to distinguish. But within a few hours, the wings grow to full size and the adult coloration is visible (NASA). Furthermore, when metamorphosis is complete, the adult fruit fly emerges from the pupal case and the fly is lightly-colored, fragile, and the wings are not yet fully expanded; the fly gets darker in color in about one hour.
Punnett squares, law of independent assortment, and law of segregation: Punnett squares are a diagram which help determine the probability of the outcomes of various physical traits on a creature’s offspring (Fernandez). Mendel had several laws that relate to this lab. One of them is the law of independent assortment. This law states that allele pairs form during meiosis. So one trait being transferred down is not related to another trait (Bailey). Yet, this is false, since some traits that are close to each other on the chromosome are separated together. This relates to the lab on how the type of eye mutation may be more common if the fly has a certain type of wing mutation. Mendel’s law of segregation states that an organism has to receive an allele from each parent (Bailey). In this lab it was used to help determine the traits of the parents. The law also states that some alleles are more dominant, so only that trait will show even if the organism has one of each trait, recessive or dominant.