Transcription factors are amongst the proteins that help regulate the cell cycle. The E2F family of transcription factors are required for the cell to progress to the S-phase. The family is involved in the transcription of proteins that are required for the DNA synthesis stage of the cell cycle. The activation of S phase genes is an important checkpoint for the cell because it commits the cell to going through the cell cycle and is the checkpoint referred to as the “point of no return” for this reason. The E2F transcription factor is typically inactivated and bound to the pRB. However, when the cell is going through the cell cycle and is ready to enter the S-phase, Cyclin D promotes the kinases CDK4 and CDK6 to phosphorylate pRB. This causes pRB to no longer bind to E2F and E2F is then capable of functioning. After being released, E2F can transcribe the necessary proteins for S-phase. As E2F is important for the initiation of S-phase, it is also important in the inhibition of the cell cycle. Should an event occur where the cell needs to stop the cell cycle, such as the DNA being damaged, the cell will not commit to the cell cycle. At that stage, allowing E2F transcription would allow the DNA damage to be replicated and passed down. Therefore, the E2F family needs to remain inactive while the cell either fixes the damage or starts cell death. E2F is needed to progress through the cell cycle, but it is closely regulated so that the cell does not start the cell cycle process without the necessary requirements.
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The cell cycle is a has many components that allow it to function properly and ensure that the cell ready to replicate and does so in a safe manner. This means that the cell needs a way to check that everything is accounted for, there has been no errors in DNA replication and the spindles during mitosis are aligned properly. For these reasons, the cell cycle has checkpoints that make sure the important processes of the various stages of the cell cycle have finished and been completed correctly before moving on to the next stage of the cycle. These checkpoints have the ability to put a hold on the cell cycle if more time is needed for the cell to catch up and is done so through the control of CDK. The stages of the cell cycle have various proteins that are capable of deactivating CDK directly or activate CDK inhibitor proteins. One of the most important checkpoint proteins in the cell cycle is p53. Described as the “guardian of the genome”, p53 is activated in cells in response to DNA damage. The transcription factor p53 activates upon the detection of DNA damage and activates the transcription of p21, which serves as a CDK inhibitor. The transcription factor is carefully controlled through posttranslational modification. In the absence of DNA damage, p53 is degraded by proteasomes, but in the presence of damage it is phosphorylated to a stable and activated state. The inhibition of G1/S CDK and S CDK by p21 is necessary to stop the cell cycle before DNA replication occurs in the S-phase of the cell cycle so that the DNA damage is not replicated in the new strand and passed along to the new cell.
The cell cycle is the process by which cells replicate themselves. This requires a mechanism to control the cell cycle system. Too much proliferation can lead to cancer, while cells remaining in a quiescent state will result in no replication and cell death with no replacement. The cell cycle operates by activating and deactivating proteins that are required for DNA replication, chromosome segregation and cytokinesis. Two of the common ways to activate and deactivate proteins is through the addition or removal of a phosphate group. These proteins are regulated by kinases, which serve as the master cell cycle regulator. Kinases phosphorylate while phosphatases dephosphorylate. Phosphorylation is not always the driver of activation and can serve to deactivate proteins as well. The main kinase in cell cycle control is the cyclin-dependent kinase, CDK. Cyclin activity is controlled through the presence of cyclin proteins and through protein inhibitors. CDK levels remain constant throughout the cell cycle. The binding partner cyclin is what changes and is being made and degraded throughout the cell cycle to control the stage that is occurring.
Dredging a pond can be quite destructive on the surrounding wildlife and environment as the pond needs to have its water’s lowered and heavy machinery and equipment needs to be brought in. The process of removing sediments and shipping them away is also a costly process. The decision to dredge a pond rests as on the immediacy of the problem and what the pond is used for. As Puffer’s Pond is a communal area for swimming, fishing and nature-walking these factors must be considered. Without dredging, the pond will continue to accumulate sediments and it will develop characteristics of a marsh. The increase in sediment will also increase the rate of plant growth in the pond and decrease fish habitat. The higher levels of sediment will also exacerbate the problem of nutrient loading from runoff which promotes plant and algae growth. Because of how the pond is used, it makes sense to dredge after sediment levels have accumulated to large levels, but the town should consider the impact this will have on the surrounding ecosystem and may want to consider an ecological impact study to ensure no endangered species depend on the pond or surrounding environment which may need to be rebuilt after the dredging process.
When people hear that all dogs are going to die except for one mother and her litter of one species, there is a gut-wrenching sadness felt by millions. Dogs have evolved with mankind to be what they are today, whether they be guides, hunters or companions. When it comes to life and death situations it is easy to rash decisions based on former experience with a certain breed, but when it comes to life and death and the good of humanity, there needs to be a more evaluation. Therefore, the Labrador Retriever must be saved, for it is not only one of the most beloved breeds for families, it is also the most versatile.
Everyone knows that a lab makes for a good pet, they are gentle giants and great for families. Clearly one of the factors that goes into choosing a breed to survive is their affability towards people and families because this is what people have come to expect from dogs. They are lovable and friendly, with beautiful coats and a matching temperament. They are loyal and dependable and easy to trains. All of these are great qualities that would be desired of the last dog breed on earth.
Beyond that, Labradors are also capable of serving humans in other ways. They are capable of being service and guide dogs, for the disabled and blind, bomb dogs, for detecting threats, and search dogs for helping track and find missing people. People have developed a world where we depend on our four-legged friends to provide services beyond stalwart companion. In a world without many of the diverse breeds that serve in these roles, we must choose one that shows versatility. Labs show this versatility and it is their patience and devotedness that allows them to excel in these roles. They are a superior breed and it is the duty of those chosen to inoculate a given mother to forgo any lesser picks rooted in passion and choose the breed that will be the best for the entirety of the human race.
This study will serve to identify a key aspect of the crab spider’s vision and whether or not the intensity of light affects its ability to perceive color. We are investigating if the light intensity will change how the background color is reflected to the spider’s eyes and whether the ommochrome pigments will match the perceived color or the color of the plate in full, natural light. By knowing if the spider’s vision can adapt to dark environments, we will better know how the vision of the spider works and how it is able to function. Crab spiders are diurnal, so it would make sense that they perceive color at full light and then are able to change color to match. But, knowing that the ommochrome pigment is in the eye and what changes the spider’s pigmentation, it is also known that there has t be some relay behind what the spider sees and how it changes. It is not known if the spider sees in the same spectrum that people do, or if the amount of light that allows it to see will allow it to match the color as spot on that would allow perfect camouflage.
Cells are able to replicate themselves identically so that they can proliferate and increase in number and decrease in size. They do this cyclically, with different stages preceding the division and then the final separation. This is known as the cell cycle. The cycle is composed of the G1, S, G2, and M-phase. These stages are when the cell is going to divide, there is another phase, where the cell is not going to divide. G0 is also known as the cell being in quiescence. The G1 phase stands for gap or growth phase. This is the start where the cell checks for nutrients, energy and DNA damage to make sure it is ready to replicate the genome and then split the cell. It preps for replication by making nucleotides and proteins required for DNA replication. The S phase is the synthesis phase where DNA replication occurs. G2 phase is another gap phase where the cell grows some more, checks that the cell completed DNA replication, and checks the DNA for damage. The M-Phase is where there is chromosome segregation and spindle assembly. This is the phase that houses the steps of mitosis and includes cytokinesis. Cytokinesis occurs at the end of M-phase, after the stages of mitosis are complete, and cleaves the two halves the cell so that they are separated and now two different cells.
Bcr-Abl presented a new challenge to treating cancer because of its newly conformed shaped. After some time, Gleevec was invented that acted as a superior treatment compared to previous attempts, earning it the moniker of “wonder drug”. Gleevec was able to competitively bind to the kinase domain on Bcr-Abl that normally bound with a different substrate that allowed it to be phosphorylated and thereby activated. Once Gleevec was introduced, the substrate was no longer able to bind and could no longer be phosphorylated. This rendered the tumor cell unable to proliferate. Because Gleevec acts as an inhibitor does not mean that Bcr-Abl is incapable of binding to the substrate that causes proliferation. It just means that this occurs less frequently. That leads to the possibility of a mutation in Bcr-Abl that increase the activity and allows for an increase in binding to the non-Gleevec substrate. This is one of the potential factors that could lead to resistance of the drug.
Antibodies are part of the body’s defense against foreign invaders. They are proteins produced by a type of white blood cell, called B cells, and like any proteins, their structure determines their function. Antibodies have a variable region that is different for each antibody that binds to a different antigen. An antigen is anything that the body does not recognize as “self” and can range from pieces of virus capsids to pieces of bacterial surface proteins. The antibody is structured in a “Y” shape and has light and heavy chains that are held together by disulfide bonds. The top of the “Y” is where there is a variable antigen binding region. The constant region of the antibody allows for consistency of response and the variable top allows for different identification of foreign bodies. The antibody gene allows for the randomization of the antigen binding amino acid structure which is what creates the variability in the region. The randomized antibody gene is created by V(D)J recombination. It is non-template directed and done by tdt polymerase which is a form of DNA polymerase.
Ommochrome pigments are a type of pigment that is present in a large variety of arthropods. The pigment is present in both the eye and the body of the arthropod. The current hypothesis is that the color of the pigment is important to the pathway for color changing insects. Crab-spiders are unusual due to their ability to have reversible color changes. They are able to go from white to yellow and back to white again. The color change in the crab-spiders was originally attributed to the carotenoid pigment (commonly produced by plants which provides the yellow/orange coloration) but the pigments responsible for the spider’s color change was later found to be ommochromes. The color mimetism that the spiders are able to replicate is able to fool the discrimination ability of bees. Bees and other flowering visiting insects are known prey to the spiders and due to the close match between spider and flower, it is suggested that the color change is a predatory adaptation. Data and research is still being gathered and conducted between the spiders and birds to test if the color change may also be the result of a defensive mechanism.