Purpose
The purpose of this lab was to investigate cell signaling between two strains of yeast- a-type and alpha-type. We observed the mating interactions between the two.
Introduction
Cell-to-cell communication, or cell signaling is an important function of cells. It occurs within multicellular organisms and between unicellular organisms. Cells can communicate with each other a few different ways, although the most popular way is via chemical signals. Yeast, also known to the science world as Saccharmoyces cerevisiae, has two mating types as mentioned earlier. The two different types communicate with each other through signal transduction pathways via secreted factors. A signal transduction pathway is a series of steps in which a message received at the cells surface is amplified through transduction which then triggers a response. In yeast cells, a-type cells have receptors that receive chemical signals from alpha-type cells. Alpha-type cells also have receptors that receive chemical signals from a-type cells. That way, when they secrete their own chemical factor, the opposite type is able to receive it. Once the two yeast cells receive the signaling factor from the other type, they begin to change their cytoskeleton in order to "grow" toward their mate. This elongation of the cell is called a shmoo.
Yeasts can reproduce sexually and asexually. In asexual reproduction, also known as cell division, both the a-type cells and alpha-type cells bud in order to produce daughter cells, or haploids. In yeast, the haploid cell can turn from an asexually reproducing cell to a gamete, or sex cell. The yeasts then stop dividing and grow into their gamete shmoo form. the yeast begin to grow toward their partner and fuse together. When the two types come together, they form a diploid zygote.
We used a transfer pipet to transfer 5 drops of yeast suspensions onto their designated plates.
Data:
Discussion
In this lab, cell communication among yeast cells were observed. There were many differences observed between the alpha type and a type strains. In the alpha-type strains, there were more budding haploid cells than in the a-type. When looking at the graphs of both the cultures, we saw that the two had several similarities in the amount of cells between the a type and alpha type cultures. The outcome showed that more budding haploid cells were seen in the alpha type than in the a type. In the alpha type, there was a much bigger percentage of budding haploid cells (12.5%) than in the a type (5%). However, when looking at the graphs for the single haploid cells, the alpha type had a lower percentage than the a type. (87.5% versus 95 %) When observing the mixed culture, which was the alpha types cells over the a type cells, we expected to see lots of budding haploid cells from the a type, and also lots of single haploid cells due to the high percentages that both the alpha type and a type had when discussing the percentage total of single haploid cells. The hypothesis was correct. When looking at the mixed culture under the microscope, it was the most abundant amount of cells observed from the three types we had looked at. Yeast cells most likely commnicate using both direct contact and pheromones. The pheremones sent help yeast spot that there is a potential mate near them, which they grow towards and then create a shmoo. Then the cellular response reacts to turn the cell into a sex cell. Direct contact signaling allows the shmoos to send a signal to create a baby (zygote).
Conclusion
In this lab, the purpose was to observe cell signaling in three different types of yeast. Looking back at the results of the expirament, it appears that the alpha type yeast has more of a mating signal released than the a-type cells. This is concluded due to the much higher percentage of budding haploid cells than type a had. Our mixed culture had the most asexual reproduction activity, which shows that the different types of yeast can communicate with eachother using direct contact and pheremones.
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