HOW PROTEINS ARE MADE BY THE CELL

TRANSCRIPTION

1. One of the strands of DNA is used as a template to create a strand of mRNA

2. Requires the enzyme RNA polymerase

3. Transcription always starts at a region called the promoter.

4. Introns are segments of DNA that do not contain genes. Exons are segments that contain genes.

5. Each 3 bases on mRNA is a codon, it corresponds to an amino acid (see codon chart, Fig 12-17)

TRANSLATION

1. Takes the message on mRNA and converts it into an amino acid chain

2. Individual amino acids will join to form a protein. Shapes and composition of protein determine its functionality (hair, enzymes, skin, muscles etc)

The steps in translation are: (Fig 12-18)
1. The ribosome binds to mRNA at a specific area.
2. The ribosome starts matching tRNA anticodon sequences to the mRNA codon sequence.
3. Each time a new tRNA comes into the ribosome, the amino acid that it was carrying gets added to the elongating polypeptide chain.
4. The ribosome continues until it hits a stop sequence, then it releases the polypeptide and the mRNA.
5. The polypeptide forms into its native shape and starts acting as a functional protein in the cell.

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