Lab Report On Fruit Fly
Introduction
Gregor Mendel, an Austrian friar born in the early 19th century, is known as the founder of modern genetics. Through his work on the pea plant (Pisum sativum), Mendel unearthed the fundamental laws of inheritance. Mendel hypothesized that phenotypic characteristics are determined by hereditary “factors”, which are now known as genes and each gene possesses two alternative forms, known as alleles. From these observations, he developed the Law of Segregation, Law of Independent Assortment, as well as the principle of dominance. In the early 20th century, Thomas Hunt Morgan, an American biologist, began experimenting on Drosophila melanogaster, a common fruit fly. Through his work on D. melanogaster, Morgan elucidated the chromosome …show more content…
theory of inheritance, for which he received a Nobel Prize in 1933. Furthermore, Morgan defined D. melanogaster as a major model organism for genetic analysis due to its short generation time, large number of progeny, adaptability to a laboratory environment and relatively small genome (Williams & Rudge, 2015).
Drosophila melanogaster’s life cycle has a duration of approximately 10 to 15 days, with offspring becoming sexually mature in one week. The life cycle begins with the fertilization of the egg, resulting in a diploid zygote, which forms the blastula through cell division. Then, the blastula gastrulates, which results in the formation of the embryo. The process of fertilization to gastrulation necessitates approximately two minutes, with the embryo emerging 10 to 24 hours following fertilization. The embryo undergoes successive alterations through the three larval stages. Following the pupal stage, the adult fly develops. In the laboratory, D. melanogaster is cultured in containers, which enclose a nutritious medium composed of agar, cornmeal and sugar (Reaume & Sokolowski, 2006).
The flies observed may be wild-type, which is the normal phenotype found in a natural population of the organism, or mutant.
The wild-type D. melanogaster possesses large and round wings, red eyes, and a grey body color. Mutant organisms may display differences in wings (apterous, miniature, vestigial), eye color (sepia, white), or body color (ebony) (McGill University, 2017).
The objective of this experiment is to cross mutant fruit flies and examine three traits (wing shape, eye color and body color) of the F2 generation to determine their mode of inheritance; whether they are sex-linked or autosomal, and recessive or dominant, utilizing the Chi-square statistical test, which compares observed and predicted results, and to ultimately determine the genotype and phenotype of the parents.
In this experiment, given the nature of a dihybrid cross, the following hypothesis was formulated. According to Mendel’s Laws of Inheritance, the F2 generation of a dihybrid cross involving two traits of a homozygous recessive mutant and a homozygous wild-type is expected to yield a phenotypic ratio of 9:3:3:1. To evaluate whether the experiment follows the Mendel Laws, the null hypothesis (H0), a method of statistical analysis, states that the observed ratio of the phenotypes does not differ significantly from the expected ratio if the p-value is superior to 0.05 (Pierce,
2016).
Materials and Methodology
During the first week of the experiment, the F1 generation was observed. The jar was gently tapped to allow for displacement of the flies and FlyNap®, which puts the flies to sleep for 50 minutes to several hours, was used as anesthesia. The anesthesia wand was dipped lightly in the FlyNap® and inserted gently into the vial for approximately two minutes, while avoiding touching the borders, to put the flies to sleep without harm (Carolina Biological Supply Company, 2016). More than two minutes’ exposure to FlyNap® is dangerous to the flies. Thus, if the walls of the jar are contaminated with FlyNap®, they should be wiped off. Once the flies were noted to have slower activity, they were transferred to a white sheet of paper and their traits were examined under the dissection microscope, and the phenotype was recorded. Five males and five females (1:1 ratio) were placed back into the vial. The F1 flies were cultured at room temperature in vials containing nutritive media (agar, cornmeal, sugar) to allow for fertilization, egg hatching, and growth of the F2 generation to occur. After a week, the larvae of the F2 generation began to appear. The F1 generation was removed from the vial to avoid mating between the F1 and F2 generation. The sex and phenotype of the F2 generation were determined through observational data collection over a period of 7 to 10 days. Following the recording of the traits of a fly, the organism was disposed of to prevent counting the same fly twice and potentially skewing the data. A total of 250 F2 generation D. melanogaster flies were observed throughout this period under the dissection microscope. The Chi-Square value was calculated, and the p-value was determined, to conclude whether the null hypothesis was accepted or not.
Gregor Mendel, an Austrian friar born in the early 19th century, is known as the founder of modern genetics. Through his work on the pea plant (Pisum sativum), Mendel unearthed the fundamental laws of inheritance. Mendel hypothesized that phenotypic characteristics are determined by hereditary “factors”, which are now known as genes and each gene possesses two alternative forms, known as alleles. From these observations, he developed the Law of Segregation, Law of Independent Assortment, as well as the principle of dominance. In the early 20th century, Thomas Hunt Morgan, an American biologist, began experimenting on Drosophila melanogaster, a common fruit fly. Through his work on D. melanogaster, Morgan elucidated the chromosome …show more content…
theory of inheritance, for which he received a Nobel Prize in 1933. Furthermore, Morgan defined D. melanogaster as a major model organism for genetic analysis due to its short generation time, large number of progeny, adaptability to a laboratory environment and relatively small genome (Williams & Rudge, 2015).
Drosophila melanogaster’s life cycle has a duration of approximately 10 to 15 days, with offspring becoming sexually mature in one week. The life cycle begins with the fertilization of the egg, resulting in a diploid zygote, which forms the blastula through cell division. Then, the blastula gastrulates, which results in the formation of the embryo. The process of fertilization to gastrulation necessitates approximately two minutes, with the embryo emerging 10 to 24 hours following fertilization. The embryo undergoes successive alterations through the three larval stages. Following the pupal stage, the adult fly develops. In the laboratory, D. melanogaster is cultured in containers, which enclose a nutritious medium composed of agar, cornmeal and sugar (Reaume & Sokolowski, 2006).
The flies observed may be wild-type, which is the normal phenotype found in a natural population of the organism, or mutant.
The wild-type D. melanogaster possesses large and round wings, red eyes, and a grey body color. Mutant organisms may display differences in wings (apterous, miniature, vestigial), eye color (sepia, white), or body color (ebony) (McGill University, 2017).
The objective of this experiment is to cross mutant fruit flies and examine three traits (wing shape, eye color and body color) of the F2 generation to determine their mode of inheritance; whether they are sex-linked or autosomal, and recessive or dominant, utilizing the Chi-square statistical test, which compares observed and predicted results, and to ultimately determine the genotype and phenotype of the parents.
In this experiment, given the nature of a dihybrid cross, the following hypothesis was formulated. According to Mendel’s Laws of Inheritance, the F2 generation of a dihybrid cross involving two traits of a homozygous recessive mutant and a homozygous wild-type is expected to yield a phenotypic ratio of 9:3:3:1. To evaluate whether the experiment follows the Mendel Laws, the null hypothesis (H0), a method of statistical analysis, states that the observed ratio of the phenotypes does not differ significantly from the expected ratio if the p-value is superior to 0.05 (Pierce,
2016).
Materials and Methodology
During the first week of the experiment, the F1 generation was observed. The jar was gently tapped to allow for displacement of the flies and FlyNap®, which puts the flies to sleep for 50 minutes to several hours, was used as anesthesia. The anesthesia wand was dipped lightly in the FlyNap® and inserted gently into the vial for approximately two minutes, while avoiding touching the borders, to put the flies to sleep without harm (Carolina Biological Supply Company, 2016). More than two minutes’ exposure to FlyNap® is dangerous to the flies. Thus, if the walls of the jar are contaminated with FlyNap®, they should be wiped off. Once the flies were noted to have slower activity, they were transferred to a white sheet of paper and their traits were examined under the dissection microscope, and the phenotype was recorded. Five males and five females (1:1 ratio) were placed back into the vial. The F1 flies were cultured at room temperature in vials containing nutritive media (agar, cornmeal, sugar) to allow for fertilization, egg hatching, and growth of the F2 generation to occur. After a week, the larvae of the F2 generation began to appear. The F1 generation was removed from the vial to avoid mating between the F1 and F2 generation. The sex and phenotype of the F2 generation were determined through observational data collection over a period of 7 to 10 days. Following the recording of the traits of a fly, the organism was disposed of to prevent counting the same fly twice and potentially skewing the data. A total of 250 F2 generation D. melanogaster flies were observed throughout this period under the dissection microscope. The Chi-Square value was calculated, and the p-value was determined, to conclude whether the null hypothesis was accepted or not.