complementary base pairing
What complementary base pairing means in Biology A-Level, as defined for AQA, OCR.
Definitions of complementary base pairing
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Reference: AQA
Free RNA nucleotides align opposite exposed bases, with RNA uracil pairing with DNA adenine, adenine with thymine, cytosine with guanine, and guanine with cytosine.
Adenine pairs with thymine and cytosine pairs with guanine, with two hydrogen bonds for adenine–thymine and three for cytosine–guanine.
Exposed bases pair and hydrogen bonds form between them, holding the fragment in place but not joining the strands.
Ensures the new DNA strand is an exact copy of the original sequence, so the genetic code is copied exactly.
The bases of the siRNA pair with complementary bases on any mRNA carrying that sequence, acting as a guide.
Adenine pairs with thymine and cytosine with guanine, with hydrogen bonds forming between them.
Topics that use complementary base pairing
- DNA and protein synthesis (AQA A-Level)
- DNA replication (AQA A-Level)
- Recombinant DNA technology (A-level only) (AQA A-Level)
- Regulation of transcription and translation (A-level only) (AQA A-Level)
- Nucleotides and nucleic acids (OCR A-Level)
Related terms
- nuclear pore
- phosphodiester bonds
- promoter region
- template strand
- universal genetic code
- alternative splicing
- ATP and ADP as energy carriers
- cDNA and reverse transcriptase
Using complementary base pairing in the exam
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