enabling replicative immortality

what do cultured normal human cells have

limited capacity to divide approx. 20-70 times

what is replicative cellular senescence known as

hay flick limit

what is hay flick limit

limit to how much cells can divide

what process are telomeres important in

hay flick limit

what is senescence

a type of cellular ageing

what are telomeres

protective caps at the end of repetitive DNA at the end of chromosomes and consist of hexametric TTAGGG nucleotide repeats and a protein complex (shelterin)

what do telomeres do

keep chromosomes from unravelling

what does the prevention of chromosomes unravelling prevent

• prevents chromosomes being damages or accidentally linking to each other during cell division

• e.g. like caps on shoelaces to stop them from fraying

what happens each time a cell divides

• telomeres get shorter and shorter

• eventually the ends of the chromosomes become frayed, like a frayed shoelace that’s missing its plastic cap

when is crisis point triggered

when the cell identifies that there are damaged bits of DNA

what is the result of activation of the crisis point

either a kind of long-term sleep known as senescence or death

what is telomerase

a cellular reverse transcriptase that adds DNA sequences (TTAGGG) onto telomeres to prevent shortening

what is detected in 85-90% of all malignant tumours

up regulation of telomerase

what do tumour cells by pass

• the crisis point by up regulating telomerase and avoiding cell cycle checkpoint genes

• IMMORTILASTION

what are the most common point mutations in cancer

telomerase promoter mutations

what is an important therapy for cancer and age-related diseases

telomerase and regulation of temolere length