Here are the questions related to PROTEIN SYNTHESIS for Lv3 Biology external exam. Only some questions are answered. 
Q1. The information carried by DNA controls protein synthesis. Protein synthesis includes transcription and translation. Discuss the reasons why both transcription and translation are necessary for protein synthesis.
ANSWER
Transcription: mRNA is synthesized using DNA (or a section of DNA/ allele) as a template. Must occur in the nucleus because DNA is confined there – in this way, DNA is protected. mRNA is needed so that the instructions carried by DNA (genetic code) can be delivered to the ribosome and expressed as a specific protein.
Translation: mRNA carries the code (sequence of bases) from DNA to the ribosome, where amino acids are joined to produce a protein and polypeptide. mRNA attaches to a ribosome in the cytoplasm, tRNA molecules bring amino acids (their order determined by the anticodon of the tRNA which matches the codon of the mRNA. Amino acids are joined on the ribosome (peptide bonds). tRNAs ensure that the genetic code is accurately translated into a sequence of amino acids in the polypeptide. Translation ensures that the instructions on mRNA are accurately interpreted, and protein beings and ends at the correct points.
DNA carries the genetic code. It is kept safe in the nucleus (protected by the nuclear envelope and histone proteins). However, to be expressed (genes used to make proteins), DNA must unwind. mRNA is made as an expendable, temporary carrier of genetic information. It is used to make the polypeptides. mRNA has a relatively short life expectancy and more mRNA can be manufactured when needed. Transcription must precede translation, but both are needed if a protein is to be produced.