Five Sterile Petri Disheses

Abstract
Mutations play an important role in evolution that introduces new branches to the diversity of life. This experiment was conducted to understand the relationship between the length of exposure to the UV to the rate of mutations and the growth of bacterial cultures. Five plates containing microscopic organisms were arranged and exposed to various lengths of UV light. The test was a quantitative test to effectively the rate at which changes happen at the distinctive length of UV introduction. As the exposure time of UV light increased, the red-pigmented bacteria colonies turned white due to mutation.Therefore, both growth and mutation in the bacteria are negatively affected by increasing exposure of UV light. Consequently, both development and
mutations in the bacterial settlements are negatively influenced by expanding exposure of UV light.

Introduction
The changes that occur in hereditary material such as DNA or RNA are called mutations. Mutations can have a variety of effects on the fitness of the organism and can be caused by many variables.In other words, most mutations are random in terms of their fitness. random mutation plays a critical role for species to change over time. While other evolutionary processes as in natural selection and genetic drift tend to reduce genetic variation, mutation alone draws the opposite effect by introducing new alleles to the gene pool and increasing heritable variations within an evolving population.
UV radiation is one “exogenous agent” that causes DNA damage and due to this, mutations occur within an organism (Bertram 2000). Some mutations can be silent, which means that there aren’t any evidence of any mutation or effect. Furthermore, there are some mutations that can cause change in observable traits or the organism. These mutations can occur due to multiple reasons, such as exposure to radiation or a chemical. Other mutations are spontaneous and thus cannot be identified as to why they actually occur in the first place.

In this experiment we used bacteria which is defined as a unicellular organism. The bacteria is exposed to different durations of UV light to understand the effects. The primary goal was to see a mutation in the cells within the bacteria colonies due to the single factor of UV light being introduced. UV light exposure was set to each culture of unicellular organisms at the increasing length of time. This lead to the hypothesis that as the amount of UV light the bacteria is exposed to increases, then there will be a change in pigment color due to mutation. The null hypothesis would indicate that the UV light has no effect on the color of the bacteria colonies and thus no effect on mutation and growth.

Methods & Materials
Five sterile petri-dishes, the UV light box, a plain agar, an applicator stick, and bacteria were used to prepare five developing plates toward a week of incubation.
Five sterile petri-dishes were each labeled with the time that the plate would be exposed to UV radiation (0 seconds or negative control, 15 seconds, 30 seconds, 45 seconds, and 60 seconds). Aseptic technique was critical during each transfer of agars. Plain 50 agar was poured equally to each plate labeled. A cotton end of the applicator stick was wet with the liquid culture of bacteria, Serratia marcescens, and applied on the surface of agar the same way it was carried out to cover the agar gradient in the first part of the experiment. Plates were prepared for the UV exposure. It was in this step that each plate was separated into five different treatment groups. Each plate was exposed one at a time to the radiation according to the time labeled on the cover. Immediately after removing plates from the UV box were wrapped the plates in foil to prevent any light from entering the plates. Photo-activation of DNA repair mechanism could usually reduce the damage by the UV radiation and might introduce an undesirable variable to the
result.
This experiment starts with five plates being prepared and labeled with their corresponding time of exposure they will have to UV light. We used one control group, which was the dish that would receive no expose to UV light, in other words 0 seconds. The other four dishes continued with intervals of 15 seconds. In total we had 5 dishes labeled 0 seconds, 15 seconds, 30 seconds, 40 seconds, and 60 seconds. WHen applying the bacteria to the plates, we used the aseptic technique which means using practices and procedures to prevent contamination from pathogens. THe aseptic technique prevents contamination, that can affect the final results of the experiment. Each plate is smeared with Serratia marcescens bacteria. In order to prevent contamination, the cotton applicator stick is unwrapped from its packaging from the side opposite the cotton. To apply the bacteria on the plate, the tip of the applicator stick is placed in the tube containing the liquid bacteria culture and once wet; the swab is removed from the tube. The dishes and lids are handled with care and made sure that that they do not come into contact with any other bacteria. We do this by using gloves and making sure that either the dishes or the lids are set to any other surface. . The swab is placed on the plate and is gently smeared on by following an up and down zigzag movement across the plate. Next, to ensure even growth of the bacteria, the same movement is replicated from left to right on the plate. This technique is replicated for each plate.