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Tetrad Analysis

Submitted by rmirley on Thu, 04/19/2018 - 22:01

For the tetrad dissection crosses, since it is now known that HB1 and HA2 complement each other, their genotypes were able to be figured out at (ade1-/ade2+) for HB1 and (ade1+/ade2-) for HA2. Knowing this information, the parental ditypes (PD) can be determined as (ade1-/ade2+) and (ade1+/ade2-). This means that the non-parental ditypes (NPD) are (ade1+/ade2+) (ade1-/ade2-) and the tetratypes (TT) are (ade1+/ade2-), (ade1-/ade2+), (ade1+/ade2+), and (ade1-/ade2-). 

Yeast Mating Results

Submitted by rmirley on Thu, 04/19/2018 - 22:00

Once the two adenine deficient plates were incubated for a week, the results were observed. For the first plate, it was found that HA0 could grow without adenine present, while HA1, HA2, and HB1 could not. For the second plate, it was found that HB1xHA0 and HB1xHA2 could grow without adenine present, while HB1xHA1 and HA1xHA2 could not. 

Yeast Mating Procedure

Submitted by rmirley on Thu, 04/19/2018 - 21:59

Two adenine deficient plates were then divided into four sections each. The first plate was labeled with HA0, HA1, HA2, and HB1, and had each quadrant’s corresponding yeast type lightly spread onto it. The second plate was labeled with HB1xHA0, HB1xHA1, HA1xHA2, and HB1xHA2, and had each quadrant’s corresponding yeast cross from the incubated plate lightly spread onto it. For the spreading process, a clean toothpick was used to drag a small amount of the required yeast in a straight line near the edge of the plate. Then a new toothpick was used to drag a single line up from the first line of yeast cells and then spread them in a zig zag fashion. The goal of this process was to spread the yeast cells to roughly one cell thickness. The two adenine deficient agar plates were then left to incubate at 30oC for a week.

Tetrads

Submitted by rmirley on Thu, 04/19/2018 - 21:58

Tetrad analysis is also a valuable tool in determining the genotypes of certain phenotypes, as well as linkage between two genes. If linkage is occurring between genes then the NPD is very rare to see compared to the PD and TT. If linkage is not occurring then the ratios of PD:NPD:TT are roughly 1:1:4. Once linkage has been determined and the ratios have been confirmed, it is easy to determine which phenotype is PD, NPD, or TT and simply match it to the correct genotype. 

Mutations

Submitted by rmirley on Thu, 04/19/2018 - 21:57

Mutations can be located at several different locations on a gene. Despite being able to be located at several different points on a gene, different mutations can lead to the same phenotype. Sometimes mutations occur at the same location of a gene, so when two organisms with the same mutation mate the mutation persists to the next generation. Sometimes two organisms will display the same mutated phenotype but will have mutations at different locations from one another. When mated together, the offspring of these two organisms will no longer display the mutated phenotype, resulting in a process called complementation. 

Yeast Mating Abstract

Submitted by rmirley on Thu, 04/19/2018 - 21:56

Mutations can occur at several locations on a gene yet result in the same phenotype. Yeast are a good organism to study the heritability of mutations because of their small size, easy and quick growth, and easily definable phenotypes. These factors also make yeast good for using tetrad analysis to determine genotypes. To study this, several crosses were carried out on adenine deficient agar plates to see what haploid gametes and what diploid cells could survive without adenine present. It was found that HA0 is the only haploid yeast cell that can grow without adenine, while HA1, HA2, and HB1 cannot grow without adenine. HB1xHA0 and HB1xHA2 were able to grow without adenine present, while HB1xHA1 and HA1xHA2 were unable to grow without adenine present. These results occurred because of the locations of the mutations on the gene, resulting in dominant alleles, mutation matches, complementation, and non-mating. A tetrad analysis was then taken of HB1xHA2. The results of the analysis show that there is a roughly 1PD:4TT, with three unknown tetrads due to culture deaths. While the analysis showed the correct ratio of PD:TT, it cannot be confirmed if the genes are linked or not due to the undefined tetrads. 

Yeast Mating Abstract

Submitted by rmirley on Thu, 04/19/2018 - 21:56

Mutations can occur at several locations on a gene yet result in the same phenotype. Yeast are a good organism to study the heritability of mutations because of their small size, easy and quick growth, and easily definable phenotypes. These factors also make yeast good for using tetrad analysis to determine genotypes. To study this, several crosses were carried out on adenine deficient agar plates to see what haploid gametes and what diploid cells could survive without adenine present. It was found that HA0 is the only haploid yeast cell that can grow without adenine, while HA1, HA2, and HB1 cannot grow without adenine. HB1xHA0 and HB1xHA2 were able to grow without adenine present, while HB1xHA1 and HA1xHA2 were unable to grow without adenine present. These results occurred because of the locations of the mutations on the gene, resulting in dominant alleles, mutation matches, complementation, and non-mating. A tetrad analysis was then taken of HB1xHA2. The results of the analysis show that there is a roughly 1PD:4TT, with three unknown tetrads due to culture deaths. While the analysis showed the correct ratio of PD:TT, it cannot be confirmed if the genes are linked or not due to the undefined tetrads. 

Nyctinasty

Submitted by rmirley on Thu, 04/12/2018 - 12:54

Plants have several different types of circadian rhythm. The first is that plants orient themselves towards the sun during the day to maximize photosynthesis. Plants also undergo another circadian rhythmic nastic movement called nyctinasty. Nyctinasty is a response in higher plants to the onset of darkness. An example of nyctinasty in plants is when the leaves and petals of plants close at night. The action is brought about by darkness and is an evolutionary reaction that preserves water and sugar levels in the plant when conditions are not optimal for photosynthesis. 

Circadian Rhythm

Submitted by rmirley on Thu, 04/12/2018 - 12:53

Circadian rhythm is a biological process that displays a pattern of biological actions over the course of roughly 24 hours. All types of organisms display a circadian rhythm, including plants and animals. In animals, circadian rhythm is the animals sleep schedule. When it gets dark out the animal will get sleepy, and when the sun comes up the animal will feel energized. In plants, circadian rhythm is the plant’s orientation. Plants will reposition themselves at different times of the day in order to maximize photosynthetic output. 

LOV Domain

Submitted by rmirley on Thu, 04/12/2018 - 12:53

A LOV domain stands for a light-oxygen-voltage-sensing domain. This LOV domain is a protein sensor used by a large variety of higher plants to control phototropism, chloroplast relocation, and stomatal opening. The LOV domain has been found to do this by controlling gene expression through DNA binding. The LOV domain is also involved in redox-dependent regulations.

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