AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are important…
Full specification wording
Structure of DNA and RNA: Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are important information-carrying molecules.
DNA and RNA are nucleic acids, polymers of nucleotides, and the information they carry lies in the sequence of bases along the strand.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 1 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
DNA and RNA are nucleic acids, polymers of nucleotides, and the information they carry lies in the sequence of bases along the strand. In DNA a sequence of three bases, a triplet, codes for one amino acid, so the base sequence of a gene determines the sequence of amino acids in a polypeptide, which determines its tertiary structure and therefore its function. Because the genetic code is universal, the same triplets code for the same amino acids in almost all organisms, which is why a human gene inserted into a bacterium still yields a human protein. DNA is the long-term store: it is stable, the bases are protected on the inside of the double helix by the sugar-phosphate backbone, and it can be copied exactly.
What earns the marks
- The information being carried in the sequence of bases.
- A triplet of three bases coding for one amino acid.
- The base sequence determining the amino acid sequence, and so the primary structure, of a polypeptide.
- DNA storing the information while RNA carries a copy of it to the ribosome.
- The genetic code being universal, so the same triplets code for the same amino acids in different species.
Common mistakes and how to put them right
Describing DNA as a protein, or saying it is built from amino acids.
Writing that 'DNA is universal' when the point being credited is that the genetic code is universal.
Saying a gene codes for a characteristic rather than for a polypeptide.
Confusing the triplet in DNA with the codon in mRNA and the anticodon in tRNA.
Claiming RNA stores genetic information in all organisms, ignoring that in cells it is DNA that does so.
Exam tips
- Whenever you write 'information', say what form it takes: a sequence of bases.
- One gene, one polypeptide. Keep that phrase, because 'codes for a protein' loses marks where a protein has several polypeptides.
- In recombinant DNA questions, the mark is for the universal genetic code, so write that phrase in full.
Try the lesson
The start of the Structure of DNA and RNA: Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are important information-carrying molecules. lesson, made from checked teaching notes for this specification point.
Have a go first
DNA and RNA are both important information-carrying molecules. Which statement correctly describes how these molecules carry genetic information?
Listen
DNA and RNA are nucleic acids, polymers of nucleotides, and the information they carry lies in the sequence of bases along the strand. In DNA a sequence of three bases, a triplet, codes for one amino acid, so the base sequence of a gene determines the sequence of amino acids in a polypeptide, which determines its tertiary structure and therefore its function. Because the genetic code is universal, the same triplets code for the same amino acids in almost all organisms, which is why a human gene inserted into a bacterium still yields a human protein. DNA is the long-term store: it is stable, the bases are protected on the inside of the double helix by the sugar-phosphate backbone, and it can be copied exactly. A strong answer earns marks for these points. the information being carried in the sequence of bases. a triplet of three bases coding for one amino acid. the base sequence determining the amino acid sequence, and so the primary structure, of a polypeptide. DNA storing the information while RNA carries a copy of it to the ribosome. Exam tip: Whenever you write 'information', say what form it takes: a sequence of bases.
Key words
Say what each word means before you turn the card.
nucleic acids
Try answering aloud or in your head before turning the card.
base sequence
Try answering aloud or in your head before turning the card.
triplet code
Try answering aloud or in your head before turning the card.
universal genetic code
Try answering aloud or in your head before turning the card.
See every definition
- nucleic acids
- DNA and RNA are important information-carrying molecules, and both are polymers of nucleotides.
- base sequence
- The information carried lies in the sequence of bases along the strand.
- triplet code
- In DNA a sequence of three bases codes for one amino acid.
- universal genetic code
- The same triplets code for the same amino acids in almost all organisms, so a human gene inserted into a bacterium still yields a human protein.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Structure of DNA and RNA: Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are important information-carrying molecules.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge