Team Members: Kevin Kasten & Jill
Amaon
Team Members: Kevin Kasten & Jill
Amaon
References & reference Images:
|
|
|
|
Comments :
What These Animations Are Attempting to Show
The first animation demonstrates the cell cycle of somatic cells, and it was created using figure 8.2 as a reference. Basically this animation is showing the four phases of the cell cycle, including G1, Synthesis, G2, and Mitosis. Starting after Mitosis is G1 of Interphase. During this stage Cyclin D and cdk 4/6 are bound together. This cyclin and its kinase are required for the continuation of the G1 phase. After separation of the Cyclin D &endash; cdk 4/6 complex, another complex forms. This complex matches Cyclin E with cdk2, and marks the beginning of the Synthesis phase. As Synthesis continues, Cyclin E and cdk2 break their complex and Cyclin A combines with cdk2. Once this occurs the cell continues until DNA synthesis is complete. Once the DNA has been copied the Cyclin A &endash; cdk2 complex degrades and the cell enters into G2. G2 is marked by the binding of Cyclin A to cdc2, as well as by the binding of Cyclin B to cdc2. Cyclin B, one of the components of MPF, accumulates during S phase and binds with cdc2 to form MPF. This complex then serves to activate mitosis by phosphorylating target proteins located within the cell. The cell enters the M phase, and upon completion, Cyclin B is degraded, and as a result, MPF is degraded. The cell enters G1 and starts the cycle all over again.
The second animation from page 224 is a more simplified view of the cell cycle, and it has to do more with blastomere cycles. It starts with Cyclin synthesis. Once Cyclin B is synthesized, it binds with activated cdc2 to form MPF. MPF initiates mitosis in the cell. Once the cell has completed mitosis, Cyclin B is degraded and MPF breaks down. During interphase inactive cdc2 builds up and waits for cyclin synthesis to begin again.
The last animation involves the two mitotic blocks that were discussed towards the beginning of the semester. The start of the animation shows the cell at the first cell block, which occurs at G2 prophase. The cell arrests at this Diplotene block because it lacks MPF. To combat this progesterone is released by the female body. Progesterone directs the egg to polyadenylate the c-mos mRNA, which then produces the c-mos protein. The purpose of c-mos is to activate a phosphorylation cascade resulting in the activation of p34 on the MPF complex. Active p34 allows the active MPF complex to initiate the break down of the germinal vesicles, allowing chromosomes to divide.
Upon completion of the first block the egg encounters a second block, as demonstrated by the animation. This block occurs in the second meotic metaphase, hence the title 'Metaphase Block'. CSF is thought to be the reason for the blockage, and is believed to prevent continuation of the cell cycle by blocking the degradation of cyclin. CSF is a complex of c-mos and cdk2. In the animation, the breaking of the block is shown to be initiated by fertilization. When the sperm enters the egg there is a flux of calcium. This calcium flux activates Calmodulin, a calcium-binding protein. Calmodulin's role is to activate two enzymes, Cam-PKII and Calpain. Cam-PKII inactivates p34, while Calpain serves to degrades c-mos. Once CSF is degraded through the inactivation of p34 and c-mos, cyclin is able to be degraded and the meiotic cycle is able to be completed.
Assumptions Made For These Animations
Assumptions made in these animations mainly include the scale sizes and appearances of the different cyclins and protein kinases. Another assumption included the time frame for these different cycles. The animations are meant to show the overall process, not really with scaled size or timing.
What Can be Done to Make the Work Better
A better animation could be generated for all cycles if more pictures were taken. Taking more pictures would allow for more detail to be demonstrated. If each complex were shown actually coming together and forming in a series of frames, that would greatly add to the animation. Also, by taking more pictures, a better sense of movement between the different stages could be revealed. An example would be showing both the binding of Cyclin B to cdc2, as well as its dissociation upon the completion of Mitosis. Adding more detai, and increasing the number of overall frames would be good ways to improve this animation in the future.
