Protein Synthesis (SNAB Topic 2)

Transcription takes place in the nucleus. The DNA double helix unwinds and hydrogen bonds between the bases break, allowing the two strands to partly separate.

The sequence on the template strand is used in the production of the mRNA molecule. The mRNA is built from free RNA nucleotides which line up alongside the DNA template strand. The template strand is also known as the antisense strand, because it makes an mRNA molecule with the same base sequence as the DNA coding strand (sense strand). 

The order of bases on the DNA determines the order of bases on the RNA (complementary base pairing). Every triplet code gives rise to a complementary codon on mRNA.

During this process, enzymes such as RNA polymerase are used to produce the RNA. The completed messenger RNA molecule leaves the nucleus through a pore in the nuclear envelope and enters the cytoplasm, where stage 2 (translation) takes place.

Translation takes place on ribosomes. Ribosomes are small organelles made of ribosomal RNA and protein. They are found free in the cytoplasm or attached to endoplasmic reticulum.  

A transfer RNA molecule (tRNA) carrying an amino acid has three bases called an anticodon, and these pair with complementary bases on the mRNA codon.

Then, the amino acids that the tRNA carry are joined by peptide bonds.

In short: 

DNA sense strand (also known as the coding strand)

DNA antisense strand (also known as the template strand) 

> transcription of antisense strand

mRNA

> translation of mRNA 

Protein