Structure of DNA and RNA 2.6

DNA is the long molecules which makes up the genetic material in all cells. It is made from smaller units called nucleotides and in this topic a knowledge of the structure of nucleotides of DNA and RNA is required, as is a simple understanding of the structure of the double stranded, double helix, DNA.

Key concepts

Essentials

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - good revision for all students.

Read the slides and look up any words or details you find difficult to understand.

Summary

Summary list for 2.6 structure of DNA and RNA

  • DNA and RNA are polymers each made of nucleotides.
  • A DNA nucleotide is made from phosphate, deoxyribose (pentose sugar), and nucleotide bases (T, A,G,C)
  • RNA nucleotides are made from phosphate, ribose (pentose sugar) and nucleotide bases (U, A, G, C)
  • Base pairing is "complementary"
  • DNA is a double helix made of two strands of nucleotides linked by hydrogen bonding RNA is a single strand of nucleotides.
  • Students should be able to draw simple diagrams of DNA and RNA nucleotides - using simple shapes (not chemical symbols). Two antiparallel strands of DNA showing base pairing. A 'ladder' structure is enough.
    Details of purines / pyrimidines are not required at SL.

Mindmaps

This diagram summaries the main sections of topic 2.6.
Test if you can draw something like these concept maps from memory.

Exam style questions

Exam style question about DNA structure

Understanding the structure of DNA and RNA is an important skill from this topic.

Answer the question below on a piece of paper, then check your answer with the model answer below.

Draw a simple diagram showing the structure of a short piece of RNA made of three nucleotides  [4]

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Extra exam question on DNA structure   --- click the + to open it. -- >

This question requires knowledge of the relationship between DNA structure and function.

The diagram shows the structure of DNA

a) Annotate the diagram to show a nucleotide (1 mark)

b) Describe what the dotted lines represent (1 mark)

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Test yourself

This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding.


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Drag and drop activities

Test your ability to construct biological explanations using the drag and drop questions below.

 

Test your construction of biological explanations using the drag and drop questions below.

The structure of DNA.

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G-C uracil monomer nitrogenous base guanine covalent nucleotides hydrogen phosphate ribose pentose complimentary backbone

Nucleic acids are polymers of .

The nucleotide consists of a sugar (deoxyribose in DNA or in RNA), a group and a (adenine, , cytosine and thymine.

The phosphate and sugar join in sequence with bonds to form the .

The bases form a base sequence on the inside of the molecule, bonded in base pairs (A-T, ).

Examiner hint: An annotated diagrm can be used to answer a question on the structure of DNA.


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