lecture 2 Flashcards
What is the hayflick limit? and what does it show?
At around 40,50,60 generations/divisions cells stop dividing . (Phase III)
This shows that most eukaryotic cells have a limited lifespan, even when nutrients are provided
What is cell senescence?
Where the cell can no longer replicate, but isn’t dying either. It is explained to be stuck in the G1 phase
Limited cell divisions stops cells from over dividing (i.e tumours/cancer)
How is this prevention related to chromosomes?
At the end of all chromosomes there are telomeres.
When cells are dividing, and chromosomes are being replicated the telomere end is missed out - it isn’t replicated.
As divisions continue the telomere ends shorten and shorten until they get too short that the cell is unable to copy the chromosome.
Why can tumour cells replicate endlessly?
This happens because tumour cells can rebuild their telomeres using the enzyme telomerase.
This enzyme is used in stem cells which continuously go through mitosis.
What are HeLa cells?
HeLa cells are cervical tumour cells isolated from a woman named Henrietta Lacks in 1951.
When isolated, it was found that some of the cells were immortal and could replicate indefinitely.
These then became the first human cell line and are still one of the most widely used cell models to day.
They were used to test the first polio vaccine in the 1950s
but they can contaminate other cell cultures.
How can we now generate cell lines
Immortal cell lines can now be formed by transforming normal cells with a viral gene (e.g SV40 virus - simian 40 virus)
This means we no longer need tumour cells
Why is phenol red dye used in cell cultures?
Phenol red dye is used to measure the pH of the culture as wastes and toxins build up. When the media turns yellow this highlights a build up of waste so that cells can be transferred to a new media.
What are adherent and non-adherent cells?
In the body, most cells are adherent (extracellular matrix) and thus also adhere to the dish/media as well.
When capacity is at its limit, the cells need to be split and detached, using the enzyme trypsin, and moved to a new dish.
This process is known as passing and occurs 1-2 times a week.
Other cells (i.e blood cells and leukaemia cells) grow in suspension, they are non-adherent.
Why do cells need to be cultured in aseptic conditions?
Because growth conditions for cells are also ideal for growth of bacterial cells.
How are conditions kept sterile?
Through the use of antibiotics in culture media, laminar flow cabinets and incubators at the correct temperature (37 degrees).
