Appreciating How the Function of DNA Was Determined
- DNA was actually 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
- However, many scientific researchers at that time 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
- For example, some scientists hypothesised that genetic information must be carried by proteins, which show much higher levels of chemical complexity
- For example, proteins are which are made up of 20 different amino acids whereas DNA is made up of only 4 different nucleotides
- As a result, 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 had 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 Tip
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!
