Then and Now series: Biochemistry in the 80s: "DNA and Protein Synthesis"

May, G. (2015) Then and Now series: Biochemistry in the 80s: "DNA and Protein Synthesis". [Website]

Abstract

This video made in 1987 and titled ‘DNA and Protein Synthesis’, is split into three sections. These sections are loosely connected to each other and can easily be viewed in isolation, however, parts 1 and 3 provide historical perspectives supporting the molecular concepts described in part 2. Part 2 of the video, entitled ‘Mechanism of protein synthesis’, gets to the heart of the matter and describes what Francis Crick had originally termed ‘The Central Dogma’. It clearly describes the basic structure of DNA and how the 4 nucleotides are used in triplets to encode the sequence of amino acids in a protein. It nicely illustrates how DNA is transcribed into messenger RNA and how this is translated (with the help of ribosomal and transfer RNAs) into protein. Although the animation is a little dated and the narration a bit slow, this information remains central to biochemistry, molecular biology and genetics and all biology students will need to understand this process. What it doesn’t describe, because this was not known about at the time, are the multiple other types of non-coding RNAs that regulate gene expression; in particular, the very small RNAs (called microRNAs, only about 22 nucleotides long), that act to inhibit the production of protein. The first part of the video shows an experiment to demonstrate that protein is made from amino acids, by components present in the cytoplasm of a cell. Thirty years ago, this could only be accomplished in the laboratory by radio-labelling amino acids and ‘following’ the radioactivity. Therefore, much of the video comprehensibly explains the nature of radioisotopes and how they can be detected. While radioisotopes are still used to some extent in biology labs today, for most applications they have been supplanted by safer, better and more versatile methods to label biomolecules. For example, proteins can be detected directly using fluorescent labels or using antibodies to specific proteins. The labelled antibodies can then be visualised by fluorescent, chemiluminescent or even infra-red methods. DNA sequencing methods have massively advanced since the making of this video, when sequencing 400 nucleotides required a full day and a big acrylamide gel, using radioactive nucleotides (as shown). Now 2nd ‘next generation’ sequencing methods permits the parallel sequencing of thousands of molecules, using optical methods of detection (including fluorescent or luminescent labelled nucleotides) or non-optical methods, for example detection of hydrogen ion release. This area continues to progress at a pace, and 3rd generation methods, including labelling nucleotides with heavy elements (such as halogens) and detection by atomic force microscopy is just one approach of many under development. The third section of the video describes a classical experiment to show that DNA, and not protein, carries the heritable information of a cell, a fact that we all take for granted now. In the early 1950s, before the structure of DNA was known, it wasn’t clear how heritable information was passed on and it was not easy to find out. To understand how the 1952 Hershey and Chase experiment was conducted, some knowledge about viruses that infect bacteria (bacteriophages) is required, which the video provides. Again, radioisotopes are used to label and track the bacteriophage DNA. The Hershey-Chase experiment is still mentioned in passing during undergraduate degree programmes in the biomolecular sciences. It is an excellent example of the use of radioactivity in molecular biology, and is of particular historic interest for anyone who wants to learn more about ‘how on earth did they find this out’. Watching this video will not only teach you some basic concepts in molecular biology, but also demonstrate some aspects of the techniques that were used to unravel those concepts.

• Item Type: Website
• Status: Published
• Refereed: No
• Glasgow Author(s) Enlighten ID: May, Dr Gerhard
• Authors: May, G.
• Subjects: L Education > LA History of education; L Education > LB Theory and practice of education > LB2300 Higher Education; Q Science > QH Natural history > QH345 Biochemistry
• College/School: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing