![]() ![]() How does the ribosome ensure that the correct amino acids are joined together to make the protein during translation? We will come back to complementary base pairing in a moment…. (Remember that in RNA, there is never any thymine but it is replaced with a different base called uracil) So A=U and C≡G are the complementary base pairs between two RNA molecules.Ĭomplementary base pairing between DNA and RNA bases is essential in transcription but you do not need to know the details at this stage. You can also get complementary base pairing between RNA bases. These pairs of bases (A=T and C≡G) are called complementary base pairs because they always match up in a predictable way. This means that this is the only way they can pair up in a stable way. Why is this? Well you can see from the diagram above that A and T are held together by two weak bonds called Hydrogen (H) bonds, whereas C and G are held together by 3 H bonds. There are four possible bases in DNA – Adenine, Thymine, Cytosine and Guanine – but they are often represented by their letters A,T,C and G.īases pair up in a totally predictable way across the double stranded DNA molecule:Ī always pairs with T, C always pairs with G. In the middle of the molecule there are pairs of bases. ![]() Let’s go back to the structure of a DNA molecule. What is meant by complementary base pairing and why is it so important? I want to end with two final questions, both of which are essential to address if you are to acquire the grade 9 understanding you need. If you are fascinated by how genetic information is encoded in DNA and how genes work at a molecular level, then you have to choose Biology as a subject to study at A level! It is a complicated topic and there is lots to understand but remember it is only one specification point out of several hundred in the IGCSE specification…… So don’t worry too much if you find this hard to grasp and don’t spend a disproportionate amount of time revising it. This is my final post on protein synthesis, you may be relieved to know…. ![]()
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