Stages of protien synthesis: Transcription & Translation

Transcription & Translation

Stage 1: Transcription

1. At the site of one gene the two strands of DNA unwind and the hydrogen bonds between the bases are broken. Catalysed by RNA polymerase. 
2. One of the DNA strands (the coding strand) acts as a template for the copying of the complimentary strand of messenger RNA. 
3. Free RNA nucleotides attach to the exposed DNA bases on the coding strand by complimentary paring. Catalysed by RNA polymerase. 
4. The DNA base sequence of the gene has been copied to a complimentary sequence of bases on the mRNA.

Stage 2: mRNA carries information to ribosomes

1. The completed strand of mRNA now leaves the nucleus via nuclear pores and enters the cytoplasm. Carrying the instructions from the DNA, 
2. mRNA moves to a Ribosome. 
3. In the nucleus, the bases on the two strands now rejoin and the DNA molecule now rewinds.

Stage 3: Translation.

1. After attachment, the ribosome moves along the mRNA strand 'Reading' the information of the codons. 
2. At the ribosomes the mRNA and the tRNA are brought closer together. So, each codon of mRNA attracts a tRNA with a complementary anticodon due to specific base paring. 
3. Peptide bonds form between the amino acids, joining them up into a polypeptide chain. 
4. The tRNA becomes detached from the ribosome, allowing the ribosome to collect another Amino acid.