2.6 Structure of DNA and RNA

Essential idea: The structure of DNA allows efficient storage of genetic information.

There is 2m of DNA in each human cell, however the most cells in the human body have a diameter of 10 μm. This DNA is divided in chromosomes and coiled around proteins called histones so that it can be efficiently stored in each cell's nucleus. The human genome project which has decoded the case sequence for the whole 2m of the human genome requires a data warehouse (pictured) to store the information electronically. This should give a good idea of just how efficient DNA is at storing information and why it needs to be so.

Understandings, applications and skills

2.6.U1	The nucleic acids DNA and RNA are polymers of nucleotides.
2.6.U2	DNA differs from RNA in the number of strands present, the base composition and the type of pentose.
2.6.U3	DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
2.6.A1	Crick and Watson’s elucidation of the structure of DNA using model making.
2.6.S1	Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases. [In diagrams of DNA structure, the helical shape does not need to be shown, but the two strands should be shown antiparallel. Adenine should be shown paired with thymine and guanine with cytosine, but the relative lengths of the purine and pyrimidine bases do not need to be recalled, nor the numbers of hydrogen bonds between the base pairs.]

[Text in square brackets indicates guidance notes]

Starter

Mr W's DNA Rap is a fun intro to DNA structure

What are the key differences between DNA and RNA?
Think back to what you have learned in other topics. Note down your answer then check the video to see if you have missed anything.

Notes and presentation

The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.

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Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

Below are the notes for this topic. Alternatively the 2.6.The structure of DNA and RNA notes - the bottom line template can be used as a note construction template in itself or as a checklist if you are using your own or another template such as the Cornell style template.

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DNA Extraction

DNA Extraction is fun, quick and can be done at home. Here are outlines from:

Model making

Use the RCSB resources to build your own DNA model. First download the pdf with the outline and instructions. To help you fold the model correctly follow the instructions in the video below:

Quick quiz

Quick quiz Use the BioK Quick Quiz on 2.6 Structure of DNA and RNA (as directed) to check your understanding of the topic.

Weblinks

DNA Structure
DNA by Khan Academy
DNA Anatomy by John Kyrk
Build a DNA Molecule by learn.genetics

Virtual labs
DNA extraction virtual lab by learn.genetics

Nature of science

Using models as representation of the real world—Crick and Watson used model making to discover the structure of DNA. (1.10)

Use the links to find out more about Crick and Watson:
How I discovered DNA by James Watson
The DNA molecule by DNA from the beginning
Discovering the double helix structure of DNA from the DNA Learning Center includes an interview with James Watson

Theory of knowledge

The story of the elucidation of the structure of DNA illustrates that cooperation and collaboration among scientists exists alongside competition between research groups. To what extent is research in secret ‘anti-scientific’? What is the relationship between shared and personal knowledge in the natural sciences?