Ribosomes are seen singly but more often lie in groups along messenger RNAs. These groups are called Polyribosomes, Polysomes or Ergosomes. Ribosomes are assembled in the nucleoli. In humans and mammals they possess a greater 60s and a smaller 40s subunit. The 40s subunit has 33 different proteins and a 1,900 base-long 18s rRNAt.
Ribosomes serve for protein synthesis involving a process called translation.
Tranlation is the realisation of the genetic information. The aminoacid sequence of the synthesised protein corresponds to the copy of the genetic code present in the m-RNA attached to the ribosome. Proteinbiosynthesis is present during the G1-phase of the cell cyclus, the phase of proliferation that belongs to mitotic interphase. After delivery of its aminoacid a t-RNAs leaves the ribosome to give space for the next one while the protein is elongating. Since many ribosomes are seen along one m-RNA many molecules of the same protein are synchronously syntetised.