Protein Synthesis

DNA is able to create protein through protein synthesis. Even though DNA contains information that encodes protein, DNA molecules cannot go out the nuclear membrane because their shape is too large. Therefore, DNA is transcribed into mRNA. First, the DNA strands are replicated. RNA polymerase reads DNA from 3’ to 5’ and synthesizes a strand of messenger RNA in the 5’ to 3’ direction. In mRNA, every 3 RNA bases form a codon. In the processing of RNA, introns, which are noncoding parts of DNA, are cut out via splicesomes. Only exons are left. A G-cap (Guanine), is put on the mRNA to protect the message. And a poly A tail with many A nucleotides is added as well. In translation, mRNA is first decoded to produce polypeptides that make up the amino acids. The transfer RNA carries amino acids to the ribosome where proteins are processed. mRNA and tRNA make codons and anticodons match with each other in the ribosome. There are three sites in the ribosome. A site accepts codons and anticodons; P site binds the peptides; and E site makes the protein exit. Start codon is known as Met (AUG).