Every day we are exposed to and even consume carcinogens and mutagens such as caffeine, UV radiation, industrial pollutants, pesticides, food additives, and natural substances such as tobacco. Caffeine is known to be mutagenic to bacteria and fungi and can be mutagenic to mammalian cells in very high concentrations. Yeast are single-celled eukaryotic microorganisms that are commonly used as model organisms.
The purpose of this experiment was to measure the mutagenicity of different substances when exposed to Saccharomyces Cerevisiae. In our case, the substance tested was caffeine. The specific strain of yeast used was D7 in a liquid culture of YEPD (yeast-peptone-dextrose) medium. Two different trials were performed with each trial having three plates labeled Positive, Experimental, and Negative. The positive plate contained yeast cells and was exposed to a high dose of UV radiation.
The Experimental plate contained yeast cells and caffeine. The negative plate only contained yeast cells and served as our control group. The purpose of having three plates was to determine was to compare the percent mutagenesis of each plate while having different variables and a control. The experiment resulted in yeast cells having a minute percent mutagenesis when exposed to caffeine. The yeast cells in the negative plate or control group did not mutate at all. The yeast cells in the positive plate had a much higher rate of mutation.
Saccharomyces cerevisiae, also known as yeast, is used as an important model organism in the scientific research industry. Studying the biology of yeast cells, has allowed scientists to work out connections between genes and proteins, and the functions they carry out in our cells. Yeast are single-celled eukaryotic microorganisms and many essential cellular processes are the same in yeast and humans. It is therefore an important organism to study to understand basic molecular processes in humans. Since the cellular processes are similar in humans and yeast cells, we can infer how cells will react in humans based on how they react in yeast cells.
Yeast cell manipulation is by far the cheapest and easiest way to understand these processes when compared to using other model organisms such as mice. Caffeine is the most widely used stimulant in the world and is present in a variety of products including beverages such as coffee, tea, colas, energy drinks, food products containing chocolate, some energy bars, and over-the-counter medications sold to increase alertness. Caffeine is known to be mutagenic to bacteria and fungi and can be mutagenic to mammalian cells in very high concentrations. Mutagenesis is a process by which the genetic information of an organism is changed, resulting in a mutation. It may occur spontaneously in nature, or as a result of exposure to mutagens.
A mutation is any change in the DNA code such as a nucleotide change, deletion, insertion, or chromosomal rearrangement. Different methods of testing the mutagenicity of a substance includes using the D7 strain of yeast and the Ames test. In the Ames test, any colonies of bacteria that appear on the plate contain cells that underwent a mutation such that the cells are able to grow without histidine. When exposing the yeast cells to a potential mutagen, if the cells mutated, they will become red, pink, or half red/half pink. The mutagenesis of yeast cells when exposed to different substances is being tested because this will assist in the understanding of the effects of possible mutagens in human cells. If caffeine causes mutations in yeast cells, then the cells will become red, pink, or half red/half pink.
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