Transcription, Splicing.

Overview of peptide synthesis:

• DNA provides instruction - in the long sequence of bases on the nucleotides. The order of the bases and which bases are present determined the instruction. 
• Complimentary section of the DNA is formed. This is called pre-mRNA. TRANSCRIPTION
• Pre-mRNA is spliced to form mRNA. 
• mRNA acts as template, where tRNA attaches, lining up amino acids and linking them. TRANSLATION. Forms polypeptides.

Transcription is where a complimentary section of DNA is formed, called pre-mRNA. 

1. Firstly, DNA HELICASE breaks the hydrogen bonds on a section of a strand of DNA, exposing the nuclotide bases. 
2. RNA POLYERMASE moves along one of the strands (template strand), casuing it's nucleotides to join with free nucleotides in the nucleus.
3. The strand of DNA reforms behind this. This forms a strand of pre-mRNA, and the DNA left reformed.
4. The RNA Polyermase stops attatching bases when it reaches a particluar sequence of bases, arranged as a 'stop code' 

Splicing is the transformation of pre-mRNA into mRNA. This is done by removing the introns. Introns are regions of non coding, non functional DNA. Exons are regions of coding DNA (for proteins, enzymes, polypeptides.) After splicing, translation happens. 

SO 

:- Transcription -> Splicing -> Translation. ^____^ 

DNA Helicase breaks the hydrogen bonds, RNA polymerase adds free nucleotide, DNA Helicase closes it up 12 bp behind. Strand of pre-mRNA is formed. pre-MRNA is spliced (introns removed). mRNA left over.