Apoptosis Flashcards
Identify the different ways in which the cell cycle is regulated.
The cell cycle is regulated by checkpoints in the cell cycle to ensure that a complete and damage-free copy of the genome is transmitted to the two daughter cells. If there is an error, the cell cycle will either be aborted or delayed, allowing time for the error to be corrected. Errors include unreplicated or damaged DNA and chromosome misalignment.
Explain the G1 checkpoint.
The G1 checkpoint checks the DNA before division. If DNA is damaged or incomplete, the cell will stop continuing on with the cell cycle. It will either enter the G0 stage or will be targeted for destruction by protein known as p53, a tumour suppressor protein.
Explain the G2 checkpoint.
During the G2 checkpoint, the replicated DNA (from S stage) is checked for completeness and lack of damage.
Explain the M checkpoint.
The M checkpoint occurs during metaphase in mitosis. It will check to ensure that the sister chromatids are attached to the correct spindle, and that the chromatids are pulled to opposite directions.
Define the process of apoptosis and highlight its importance.
Apoptosis is a regulated process of a programmed cell death, essentially the cell self-destructing. This is a very important process as some cells may be damaged or not suitable to continue on with the cell cycle. Damaged cells dying will lead to a higher likelihood of a healthy body/organism.
Apoptosis often occurs when there are excessive cells, damaged/dysfunctional/diseased cells, and when cells are at the end of their natural life.
What are the steps of apoptosis?
The nucleus of a cell condenses and blebs (bumps/bulges that are a result of cell injury) are formed. There is then a partition of the cytoplasm and nucleus into apoptotic bodies, and phagocytosis (the ingestion of bacteria/other materials by phagocytes) occurs.
Identify some disruptions that can occur in the cell cycle.
- An excess amount of cells/build up of cells (e.g. psoriasis)
- Cell cycle becomes uncontrolled and tumours are produced (cancer)
- Checkpoints overridden (no error detection or error correction)
- Abnormal cells with damaged DNA pass their errors to their daughter cells
- Mutation is tumour suppressor genes
Describe how malfunctions in apoptosis can lead to deviant cell behaviour with reference to cancer.
When cells do not die, they will overproduce and the cell cycle will become uncontrolled. Tumours can be produced due to this and will lead to cancer. In cancerous tissue, cells reproduce at a rate that is in excess of the normal regulated rate of the cell cycle.
Describe differentiation/specialisation.
Cell differentiation is the process by which cells
become specialised for a specific function. They lose the ability to reproduce themselves, but some cells must
remain undifferentiated to replenish cells when needed
Explain stem cells.
Stem cells are undifferentiated or unspecialised cells that have the ability to differentiate into organ or tissue-specific cells with specialised functions.
Stem cells will create copies of themselves - one will remain a stem cell for further replication, and another will become specialised.
Describe different stem cell potencies.
Potency is the ability to produce different cell types. There are four potencies in stem cells; unipotent, multipotent, pluripotent and totipotent. Unipotent cells can only develop into one type of cell (e.g. skin). Multipotent cells can develop into more than one cell type, but it is more limited than pluripotent stem cells, e.g. blood. Pluripotent stem cells have the ability to develop into one of the three primary germ cell layers. Totipotent stem cells have the ability to become any differentiated cell (e.g. zygote).
What are the sources of stem cells?
The three main sources of stem cells are; embryonic stem cells, adult stem cells and induced pluripotent stem cells.
How are stem cells used in regenerative medicine?
Stem cell therapy is the ability to control cell divisions and differentiation to generate healthy lab-cultured tissues and organs to replace damaged ones. Stem cell therapy can be used to assist in the treatment of parkinsons, type 1 diabetes, heart disease, spinal cord injuries and cancer.
What is therapeutic cloning?
Therapeutic cloning is the process of producing stem cells for use in treatment. It involves creating an embryo by somatic nuclear transfer for the purpose of obtaining its stem cells. The somatic healthy cell that provides the nucleus is the intended recipient of the stem cells - therefore, the embryo is a genetic match to the patient.
