10.1 Study Guide Flashcards
State the phases of the cell cycle in order beginning just after cell division. Which phases make up the larger section known as interphase?
G1 - S - G2 - M (cycle back to G1)
Interphase consists of the G1, S, and G2 phases.
(G0 is a phase outside of the cycle)
Give at least two examples of inhibitory cell cycle proteins. What is their function? What types of events activate them?
- p53 - Inhibits the activity of Cdk-cyclin complexes when DNA within a cell is damaged; prevents progression through the cell cycle while the cell is at high risk of mutation. It can also trigger apoptosis if all means of repair fail.
- Retinoblastoma Proteins (Rb Proteins) - Prevent the activation of cell-cycle processes when the cell has insufficient concentrations of growth factors.
Explain the purpose of Cdks and cyclins in the cell. What reaction do they perform to carry out this function? What types of proteins stimulate cyclin production?
On their own, Cdks and cyclins do little to nothing, but the two proteins can bond to form Cdk-cyclin complexes. These protein complexes are then able to perform phosphorylation with other specific proteins, exchanging phosphate groups with them and changing their structure and function. This ‘activates’ the other proteins to begin carrying out the processes performed throughout the cell cycle. Proteins that stimulate cyclin production are known as Growth Factors and are transported into the cell from elsewhere in the body.
Explain the roles of proto-oncogenes and tumor suppressor genes. What problems might be caused by mutations in these genes?
The role of proto-oncogenes is to code for stimulatory proteins such as Cdk and cyclin to power a cell’s progression through the cell cycle. The role of tumor suppressor genes is to code for inhibitory proteins like p53 and Rb proteins that pause and control a cell’s progression through the cell cycle. The normal function of these two sets of genes allows for safe and healthy cell division, but when these genes become mutated, they are unable to perform their roles and problems begin to arise. Namely, the mutation of proto-oncogenes into oncogenes often produces uncontrolled cell division that creates cancerous tumors. Additionally, the mutation of tumor suppressor genes removes the ‘brake system’ from the cell cycle and also often produces uncontrolled division and cancer.
What difference between proto-oncogenes and tumor suppressor genes affects how likely their mutations are to cause uncontrolled cell growth?
Proto-oncogenes are dominant genes, while tumor suppressor genes are recessive. This means that only one proto-oncogene needs to be mutated to produce uncontrolled cell division, but both types of tumor suppressor genes in humans need to be mutated to fully remove the ‘brake system’ and produce uncontrolled division.
What is the purpose of ‘checkpoints’ between different phases of the cell cycle?
The ‘checkpoints’ between the different phases of the cell cycle are specific criteria that the cell must meet to allow itself to continue to a new phase of the cycle. If a cell, for instance, has insufficient resources for growth or has damaged DNA, it is programmed to not progress any further until the problems have been remedied, or to perform apoptosis if they cannot be fixed.
