Cell Determination and Cellular Senescene Flashcards
What is cell determination?
Cell determination is the process where a cell’s fate becomes stable. It is then followed by differentiation, “the cell becomes determined to choose its fate”
Described asymmetrical cell division
Asymmetrical cell division is when a cell divides due to the difference in the distribution of the cytoplasmic molecules and there ends up being an unequal distribution of the cytoplasmic molecules
What causes cell determination?
Inductive signals from neighbouring cells - one cell influences the development of another group of cells
What is cellular senescence?
Cellular senescence is an irreversible cell-cycle arrest mechanism that causes cells to stop dividing
It happens as a response to excessive intracellular and extracellular stress e.g. telomere attrition, oncogene activation and oxidative stress
Cellular senescence is strongly implicated in symptoms of ageing but it is also important for defence against Cancer
What is apoptosis?
Apoptosis is programmed cell death, it does not happen as a response to anything and it plays an important role during the individual’s life as it allows for cell renewal
What morphological changes happen to a cell during cellular senescence?
-Larger and flat cells
-Prominent nucleoli
-Nuclear lamina degradation
-Vacuolated
-Chromatin reorganisation
What biological and molecular changes happen to a cell during cellular senescence?
-The molecules become marked, the two most known markers are lysosomal B -galactoside and protein p16
-The Senescence associated secretory phenotype consists of inflammatory cytokines, growth factors and proteases so they will be present during cellular senescence
What are telomeres?
Telomeres are regions at the end of the chromosomes that are composed of the TTAGGGGn DNA sequence whos function is to protect the chromosomes integrity and prevent it from damage
Desecribe Telomeric CNA
Telomeric DNA is associated with a six-member protein shelterin complex that helps the formation of DNA loops and cap/shields the chromosome ends
What is Telomerase?
Telomerase is a ribonucleoprotein enzyme which replicates its telomeric DNA by reverse transcribing the TTAGGGG DNA sequence using the RNA subunit (TERC -telomerase RNA component) and its protein component (TERT - telomerase reverse transcriptase)
Briefly explain how Telomerase elongates the telomeric DNA
- Synthesis and Transloaction
Briefly explain how Telomere shortening has an effect on cancer cells
Nearly all cancer cells have TERT so they are immortal. Telomere shortening acts as a tumour suppressor pathway however activating telomerase provides an escape from damage and allows cells to grow with a rearranged genome so they can live on
Abnormalities in cancer cells is caused by:
-Expression of TERT
-p53 defects
-p16 defects
Briefly explain how Telomere shortening has an effect on cancer cells
Nearly all cancer cells have TERT so they are immortal. Telomere shortening acts as a tumour suppressor pathway however activating telomerase provides an escape from damage and allows cells to grow with a rearranged genome so they can live on
Abnormalities in cancer cells are caused by:
-Expression of TERT
-p53 defects
-p16 defects
Examples of connections between cell senescence and ageing symptoms:
- Bone marrow - older people show decreased immunity and they have increased bone marrow failure
-Grey hair - caused by a decrease in melanocyte stem cells being maintained in the hair follicles
-The reduced healing ability of the skin - Increased risk of skin ulcers due to senescence in dermal fibroblasts
