Question

A researcher studies normal human fibroblast cells. They can be maintained in culture but die off after about 30 cell generations. Unexpectedly, a colony of cells continues to survive and divide past 30 generations. Which scenario is most likely true for these cells?

Answer 1

Human cells like fibroblast cells will grow only to a limited number of generations like 30 generations. Such cells are called finite cells or finite cell line.This is because the normal cell stops dividing when the length of the telomere of their chromosome comes to a critical length which is also called Hayflicks limit. Telomere protects chromosome ends from unwanted excision by nuclease and prevents joining of chromosome ends with each other.

A finite cell line at times get transformed to continuous cell lines that are immortal and divides beyond 30 to 50 generations. This can be due to changes in ploidy (number of basic set of chromosomes).

Such cells will have chromosomes with extra long telomeres than the normal cell chromosomes. The length of telomere increases due to continuous expression of telomerase enzyme.

The length of telomere usually will be more in cancerous cells than the normal cells. So, the fibroblast cell under study will most probably be a cancerous cell line which is called a continuous cell line. Such cells will not show contact inhibition.