Abiotic factors determine the fundamental niches of organisms.

The actual range of an organism in nature is termed the realized niche.

TLS Online TPP Program

#Id: 3237

#Unit 4. Cell Communication and Cell Signaling

miR-15-a and miR-16-1 act like tumor-suppressors;
they normally inhibit B cell proliferation

TLS Online TPP Program

#Id: 3239

#Unit 4. Cell Communication and Cell Signaling

miR-21 targets tumor-suppressor gene PTEN phosphatase

TLS Online TPP Program

#Id: 10390

#Unit 4. Cell Communication and Cell Signaling

Four stages of the evolutionary progression of cancer:

Initiation→Cancer progression → Evasion of cancer cell elimination  → Tumor growth and dispersal 

TLS Online TPP Program

#Id: 10391

#Unit 4. Cell Communication and Cell Signaling

Cancer cells 

acquire a drive to proliferate 

does not require an external inducing signal

fail to sense signals that restrict cell division

survive when they should die

TLS Online TPP Program

#Id: 10392

#Unit 4. Cell Communication and Cell Signaling

Tumors are detected only after they have reached 1cm3 in size.

TLS Online TPP Program

#Id: 10393

#Unit 4. Cell Communication and Cell Signaling

Precancerous cells have: 

lost contact inhibition

less adherent and more rounded than normal cells

continue to divide