Describe and explain the process of protein synthesis. (6 marks)

Transcription is the first step of protein synthesis. This involves DNA helicase unwinding the double stranded DNA, and complementary mRNA binding to the DNA bases with the help of the DNA polymerase. DNA ligase then binds the mRNA bases together, to form a strand of mRNA. This strand of mRNA then moves away from the DNA before undergoing splicing, where introns are removes and a poly-A-tail and 7 methylguanosine head are added. The mRNA strand then leaves the nucleus, and heads to the ribosome to begin translation. Translation begins with the joining of the mRNA strand to the ribosome. The mRNA is then read, 3 base pairs at a time, and tRNA molecules that are complementary to each codon bind, depositing their amino acids that they were carrying. This continues until all of the mRNA strand has been read, by which time tRNA molecules will have deposited many amino acids, which will join together to form a polypeptide.