Biological Aspects ? Raising Questions And Balancing Concepts

Features Of The Eukaryotic Genome
All living organisms are made of cells. Cells are endowed with the extraordinary ability to create copies of themselves during cell division, passing the information that determine the characteristics of a species as a whole and the individuals within it, through the generations. This process of replication is universal for all the different types of cells. The genome constitutes the complete store of information of an organism and it specifies all the ribonucleic acid (RNA) molecules and proteins that the organism will ever synthesize, through the processes of transcription and translation, respectively. All the genetic information is encrypted …show more content…
The ribosomal RNAs are folded into highly compact, precise three-dimensional structures that form the compact core of the ribosome and determine its overall shape and have the ability to position tRNAs on the mRNA, and its catalytic activity in forming covalent peptide bonds. The main role of the ribosomal proteins seems to be to stabilize the RNA core, while permitting the changes in rRNA conformation that are necessary for this RNA to catalyze efficient protein synthesis. The large and small ribosome subunits are assembled at the nucleolus, where newly transcribed and modified rRNAs associate with the ribosomal proteins that have been transported into the nucleus after their synthesis in the cytoplasm. These two ribosomal subunits are then exported to the cytoplasm, where they join together on an mRNA molecule, usually near its 5? end, to initiate the synthesis of proteins. The mRNA is then pulled through the ribosome, three nucleotides at a time. The small subunit provides the framework on which the tRNAs are accurately matched to the codons of the mRNA, while the large subunit catalyzes the formation of the peptide bonds that link the amino acids together into a polypeptide chain. As its codons enter the core of the ribosome, the mRNA nucleotide sequence is translated into an amino acid sequence using the tRNAs to add each amino acid in the correct sequence to the growing end of the polypeptide chain. When a stop codon is encountered, the ribosome releases the finished protein, and its two subunits separate again. These subunits can then be used to start the synthesis of another protein on another mRNA molecule. Ribosomes contains four binding sites for RNA molecules during protein synthesis. As Figure 5 shows, the process begins with a tRNA molecule is held tightly at the A and P sites of the