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Transform cells = normal cells that are made immortal through induction of viruses and therefore 'transformed

Telomerase = enzyme that synthesizes telomere (only reverse transcriptase enzyme in our body)
- not as active in normal cells, very active in cancerous cells and stem cells (cells where the tissue needs to be regenerated a lot)

Telomeres = the repetitive DNA sequences and proteins at the ends of the chromosomes
- structure changes after every replication because they are not replicated in the same way as the rest of the genome
- so when the telomere becomes too short, the cell initiates DNA damage response gives up the cells ability to divide

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Figure 20-13: Both increased cell division and decreased apoptosis can contribute to tumorigenesis 

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What causes cancerous cells to divide continuously?

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What causes cancerous cells to divide continuously?

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Replicative cell senescence = cells division speeds lsows down in as the telomere becomes shorter, until it reaches a halt where the cell enters a non-dividing state form which the cells never recover

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Figure 20-11: Loss of contact inhibition by cancer cells in cell culture

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- transformed cell line proliferates at a higher density
- normal cells aren't suspended (need to be attached to something, (cancerous cells don't need to be attached)), when they're all touching (confluence) then they don't grow anymore
- cancerous cells can keep growing even through a confluence

Transformed cell = a cell that has lost its ability to do contact inhibition,
- proliferate to a much higher density
- they no longer require positive signals in their surroundings
- respond to less signals
- finite cells = cells that can only divide finitely ... transformed cell lines are a continuous cell line
- transformed cell lines are made by inducing them experimentally with viruses (ex. a tumor indicating virus/chemical)
Contact inhibition = once the cells are in confluence they cannot keep growing

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- The first immortal cells that could grow outside of the body.
- Used for medication, treatment
- It's an epithelial cell
Immortal cell = can continuously divide
- can become immortal
- normal cells 20-40 replications, after, cell undergoes apoptosis (or sometimes becomes a senescent cells, which then leads to cell death) because telomere becomes smaller and cell reaches hayflick limit
HeLa cells can replicate forever
HeLa cells have a telomerase enzyme which keeps on growing the telomere

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https://www.hhs.gov/ohrp/regulations-and-policy/belmont-report/read-the-belmont-report/index.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860367/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3198544/

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How are HeLa cells cultured & maintained in the lab?

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How are HeLa cells cultured & maintained in the lab?

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Cells grown in culture
- different experiments that can be used in cell culture:
- in vitro = experiment on cultured cells --> glass cells in a petri dish
- in vivo = experiments using whole organisms

primary cultures = cultured cells that are taken directly from the organism which can later be used to make subcultures
- subcultures = reculturing cells from the primary cells
- subcloning = after your first subculture and primary culture becomes known as a subclone or subline (ex. HeLa cells)

- temperature needs to be very similar to body temperature
- CO2 levels need to be between 5-10%
- pH needs to be at 7. (like most mammal cells)

- important to have these conditions because in these conditions cells grow optimally AND it allows the cell to be exposed to certain experimental conditions

- we can avoid contamination of cell culture with antibiotics which prevent bacterial growth
- another technique = aseptic technique, disinfecting OR sterilization

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cDNA = complementary DNA; a DNA copy of an mRNA strand
- a short piece of DNA that encodes for a certain protein, that is taken out of a DNA
- synthesized by reverse transcriptase (which comes from retroviruses)

- start with a tissue in the body (mRNA)
- pair the poly-A-tail with a poly-T-primer on 3' end
- make complementary DNA with reverse transcriptase which creates a cDNA
- degrade RNA with RNase H
- create a double-stranded DNA by using DNA polymerase

- useful because there are no introns

cDNA clone = when cDNA is put into plasmid it can be cloned, each clone of the is a cDNA clone
cDNA library = a collection of cDNA cloned plasmid molecules

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HIV (human immunodeficiency virus) = retrovirus that attacks the bodies immune system which when not treated can lead to AIDS (acquired immunodeficiency syndrome)
- becomes AIDS depending on the number of CD4 T-cells
- retrovirus = virus that goes into the bacteria/cell and copies its DNA in the cell so that the cell keeps reproducing that DNA
- HIV infects and destroys T-cells

T cells = white blood cells
CD4 = its a glycoprotein found on the surface of immune cells like T-cells
- important for recognition the virus
- is present on T4 cells = CD4 T-helper cells which fight the virus but are then also infected by it

How does HIV enter T-cells?
- In the image (a T-cell): The T-helper cells because of CD4, recognize the HIV cell and inject its RNA (through endocytosis/membrane fusion), converted into cDNA which then enters the cells DNA
- original HeLa cells don't have CD4 receptors
- allows scientists to study the mechanism and medication for HIV

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Ethics = norms of conduct that distinguishes acceptable and unacceptable behavior

Respect for persons = individuals should be treated as autonomous
- people who have diminished autonomy are entitled to protection
Beneficence = "do no harm", maximize benefits and minimize harms
- for HeLa cells, this was not applied because used it for their own gain
Justice = "fairness in distribution"; everyone deserves the same

- informed consent = having information, what's going to happen, confidential, voluntariness
- informed consent was not applied with Henriette Lacks