Protein synthesis (simplified)

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Protein Synthesis

With thanks to Jenny P

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DNA is a very long molecule that looks like a twisted ladder.

It is made up of 4 different subunits called nucleotides which can be arranged in any order

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The bases are complementary

DNA has two strands.

The strands are stuck together by the complementary bases.

Adenine to Thymine A-T

Cytosine to Guanine C-G

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It is the Sequence of bases that act like a code

The sequence (order) of bases tells the cell what proteins to make.

The sequence of bases dictates the sequence of amino acids, which determines the shape of a protein.

If the protein is the wrong shape it will not work properly (it may work differently)

So if the sequence in the DNA is wrong it may result in a genetic disease

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Sickle cell anaemia is caused by one change in the DNA base code

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It is a triplet code.

It takes 3 bases to code for one amino acid

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Each triplet codes for a different amino acid.

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DNA carries the code for every protein that can be made by a cell.

A gene is a length of DNA which codes for a particular protein

Protein Synthesis takes place in 2 stages

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Part of the DNA molecule (the gene) unzips

An RNA copy is produced, by matching complementary bases

Transcription 1 (making a messenger RNA copy of DNA)

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Transcription 2

The mRNA copy is made with the help of RNA polymerase.

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Complementary base pairing

C

G

U

A

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The m-RNA leaves the nucleus through a nuclear pore

RNA leaving the nucleus

Nuclear membrane

RNA in the cytoplasm