The Origins of Research on the Genetic Code (AQA A Level Biology): Revision Note

Exam code: 7402

Lára Marie McIvor

Written by: Lára Marie McIvor

Reviewed by: Cara Head

Updated on

Simplicity of DNA

  • DNA was first observed in the 1800s by a Swiss scientist called Friedrich Miescher

    • Miescher is credited with being the first person to discover DNA (although he named it ‘nuclein’) and define it as a distinct molecule in 1869

  • At the time, many scientific researchers doubted that this newly discovered DNA molecule could carry the genetic code

    • They doubted this because of the relatively simple chemical composition of DNA (because DNA was only made up of simple repeating nucleotides, which themselves were only composed of three parts:

      • A phosphate group

      • Deoxyribose

      • A nitrogen-containing organic base

  • It wasn’t until the 1940s that the role of DNA in genetic inheritance began to be more fully researched and understood

  • By 1953, experiments confirmed that DNA carried the genetic code

    • It was understood that, despite there being only 4 nucleotides, the use of the triplet code enabled much variation (the code is universal and degenerate)

    • The location of DNA, protected in the nucleus, enabled the security of the genetic material rather than proteins that are found in the cytoplasm and susceptible to hydrolysis

    • DNA is easily copied and therefore conserved throughout generations of cells and inherited between generations within families

  • 1953 was also the year in which Watson and Crick confirmed the double-helix structure of DNA using Rosalind Franklin’s X-ray data

Examiner Tips and Tricks

Don’t worry about learning the dates or names given above - the main point you need to remember here is that the relative simplicity of DNA led many scientists to doubt that it carried the genetic code and that this is perhaps why the function of DNA wasn’t confirmed until a relatively long time after its initial discovery!

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Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology, Psychology & Sociology Subject Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

Cara Head

Reviewer: Cara Head

Expertise: Biology & Psychology Content Creator

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding

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