Please be very detailed so that I understand. Teacher wants all steps shown and
ID: 301120 • Letter: P
Question
Please be very detailed so that I understand. Teacher wants all steps shown and all logic justified in writing. Even if he does not ask it, he always wants to know WHY which drives me crazy or he gives you no credit.
Also, please note that this is a two part question :)
Thank you so much for the help. I am struggling so much with this subject.
Question 3 Part 1 [9 pts] The eukaryotic cell cycle is very strictly regulated with multiple checkpoints that prevent the cell cycle from continuing if certain conditions are not met A. For each of the following checkpoints, describe a condition in which cells are blocked from progressing past the checkpoint. Then, explain why each of these checkpoints is important for the cell. [2 pt each] Restriction (R) point Post-replication checkpoints Spindle assembly checkpoint B. However, when the appropriate conditions are met, the cell can advance past these checkpoints. For the R checkpoint, this requires phosphorylation of the Rb protein. How is this post-translational modification of Rb similar to the allosteric regulation we have previously discussed? How might this lead to a change in the function of a phosphorylated protein? How does the nature of a phosphate group play a role in this process? [3 pt]Explanation / Answer
3.A)
Restriction Point:
A cell's decision to enter, or reenter, the cell cycle is made before S-phase in G1 at what is known as the restriction point, and is determined by the combination of promotional and inhibitory extracellular signals that are received and processed.
Before the R-point, a cell requires these extracellular stimulants to begin progressing through the first of G1 then cell is irreversibly committed to preparing for DNA duplication. It is the cell responsibility to clear all the stimulants before it enters back in the R phase. A cell will exit the cell cycle if certain requirements to proceed to synthesis are not met.
When this checkpoint is passed, cdk4 and cyclin D interact. This interaction results in phosphorylation of the retinoblastoma protein, which in turn allows activation of the transcription factor E2F. Active E2F promotes expression of the cyclin E gene. Cyclin E (protein) and cdk 2 interact to promote the G1 to S phase transition.If there is any problem in the aboce phosphyralation and availability of the proteins the cell undergoes G0 phase.
Post Replication Checkpoint: It is a checkpoint at which the DNA is repaired afer the replication and gaps are filled in the daughter chromatids. If the repair of doesnt happen or something wrong in the replication the cell cycle is stopped.
Spindle assembly checkpoint: At this checkpoint the allignment of the spindle fibres druing the cell division is checked. We know that that is the crucial step in the cell division, becasue the spindle fibres attaches to the centromere of the chromatids and divide equally into two hemispheres of the cell.
B) In allosteric regulation the effector binds to the enzyme in restriction site other than the active site and inactivates the enzyme. Similarly in Rb phosphorylation , it restricts the DNA replication ,Rb binds and inhibits E2 promoter-binding–protein-dimerization partner (E2F-DP) dimers, which are transcription factors of the E2F family that push the cell into S phase.