When eukaryotes make mRNA, they add a 5' cap and a poly-A tail to protect the mRNA from being destroyed by ribonucleases (enzymes that break down RNA). But why do cell have ribonucleases to begin with? Why would cells to break down the mRNA it went through all the trouble to make? Use an example to explain your answer.

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.