Induction Of Mutation In Drosophila Melanogaster

Induction of Mutation in Drosophila melanogaster

Submitted by Group 8 Salumbre, Renz Salvador, Meliza Ylaine Sobrevega, Paul Christian Surquia, Joseph Michael

Submitted to Ms. Gardette Valmonte Mr. Francis Abrantes

October 11, 2007

INTRODUCTION Drosophila melanogaster, commonly known as fruit flies, are said to be the perfect organisms for investigating the principles of experimental genetics. There are many reasons why is it so, however some of the most common are 1) the convenience of culturing the said organisms; 2) it has a short generation span and that females can approximately lay 700 eggs in a single day; 3) mature larvae exhibit polytene chromosomes indicative of the process of transcription and other gene activity; 4) its inherent quality in that it contains only three autosomes and one sex chromosome. In this experiment, formaldehyde was used as an inducer of mutation. It is the simplest member of the aldehyde family with the formula CH2O and is usually employed as a disinfectant and a preserving solution. Its typical characteristics are its pungent smell, flammability and solubility in water. Frequency of mutation in the fruit flies has been well documented. Mutation, as an event that gives rise to heritable alteration in the genotype, in the fruit flies may be classified as dominant or recessive; visible, lethal or biochemical. Visible mutations are essentially identified as the loss of a function or a structure resulting in an observed difference in the morphology of the organism. Lethal mutations, however, are the ones that cause immediate death of the organism since the mutation has occurred during embryonic development. Lethal mutations are also known as chromosomal aberrations or mutations. Lastly, biochemical mutations are usually connected in relation to the organism’s enzymatic reactions. It may mean as the loss of ability to synthesize an essential metabolite. Biochemical mutations underlie the principles of visible and lethal mutations. In this experiment, the objectives were to induce mutation using formaldehyde and to compare the degree of mutation in three different concentrations of formaldehyde.

MATERIALS AND METHOD In the experiment, the materials that were utilized were the following: four sterilized culture bottles; strips of filter paper; ripe saba; yeast; propanoic acid; cotton plugs; formaldehyde and the fruit flies. The methodology first consisted of preparing the culture bottles. Ripe saba bananas were mashed and divided into four equal parts (corresponding to the four culture bottles). Then the preparation of formaldehyde was performed by deriving the concentrations of formaldehyde in each bottle using the formula C1V1 = C2V2. The different concentrations were then applied to the four culture bottles and labeled as 0%, 0.1%, 0.2% and 0.3%. Five pairs of fruit flies were inserted in each bottle and considered as initial parental generation or P0 generation. The fruit flies were then allowed to reproduce until the first filial generation and the progeny of P0 etherized using chloroform. Observation of mutations was done using a dissecting microscope or a magnifying glass. RESULTS AND DISCUSSION To reiterate, mutation is a random change in a gene or chromosome resulting into a new trait or characteristic that can be inherited. It can be a source of beneficial genetic variation or it can be neutral or harmful in effect. Furthermore, mutation can be obtained either by inducement or just by spontaneous occurrence. The former is caused by intentional addition or exposure of mutagens, such as UV rays, x-ray radiation and chemicals that can react with the DNA of an organism. On the other hand, the latter, refers to DNA damage that results from naturally occurring alterations within the genetic information. These are deletions and insertions, which can give rise to certain damages to the whole organism. In the experiment, an induced mutation was applied by simply exposing the fruit flies into four different concentrations of formaldehyde, namely 0%(controlled), .1%, .2% and .3%. The volume of formaldehyde to be added was calculated in accordance to the volume of the medium (saba) to be used using the C1V1=C2V2 formula, to obtain the

right ratio of the two substances to be mixed. Based on the fruit flies that have been gathered, 3 major observations can be obtained. First, there is a relatively low number of population of flies in the experimental bottles compared with the control. It can be deduced that for every 5 adult flies being developed in the control bottle only 1 fly is grown to its adult stage from the experimental bottles, giving a 5:1 ratio. Second, in relation with the first, the growth of the flies tend to linger most of its time at its pupa stage, having a reduced number of adult flies. Lastly, some of its pupa shows a different color with the normal ones and as well as most of the abdominal tips of the adult flies where filled with black pigment. Even though the protocols of the experiment did not require the determination of mutation by handling directly its gene sequence, it can be inferred that there was a minimal percentage of mutation that had happened. This is because, in spite the fact, that formaldehyde was known as a preservative, insecticide, and deodorant, still flies are able to produce and perpetuate. But its growth is in a modified manner, which is base on the adaptive mechanism that they are able to acquire as a response to the environment that they were forcibly exposed into. Moreover, within the chemical structure of formaldehyde, it was known that it can hydrolyze proteins, therefore a change with that certain function of protein within the flies’ DNA can lead to the process of producing genetic aberrations, that can be lethal. Furthermore, its lethality can either be based on its gender or just by its dominance or recessiveness regardless of its gender that may have affected the number of our progenies. Consequently, this will all be surely expressed unto its phenotypic characteristics, covering both of its growth and development. REFERENCES Cook, H. Molecular characterization of an unknown P-element insertion in Drosophila melanogaster. Laboratory Manual, 2005. Levine, R.P. Genetics. Holt, Rinehart and Winston, Inc. : USA, 1962

Strickberger, M.W. Experiments in Genetics with Drosophila. John Wiley and Sons: New York , 1962.