Planet Earth and Its Environment A 5000-million year Journey

Biology in Focus, HSC CourseGlenda Childrawi, Margaret Robson and Stephanie Hollis

Blueprint of LifeTopic 16: Beadle and Tatum 1DOT POINT(s)analyse information from secondary sources to outline the evidence that led to Beadle and Tatums one gene one protein hypothesis and to explain why this was altered to the one gene one polypeptide hypothesis.Introduction The phenotype of an organism is its total appearance determined during development by an interaction between its genetic make-up (genotype) and the environment. themetapicture.com

Introduction A genome is all of the genetic material (DNA) within a cell and is specific to each organism. Genomes influence nearly all the traits or phenotypes, such as eye colour, height and susceptibility to disease, and most variations occur due to differing genomes.www.rsc.org

Introduction The phenotypic appearance is therefore directly affected by gene expression. The extent of phenotypic differences depends on how different the DNA sequences are in individuals, but may also be influenced by the environment. To what extent differences in genotype cause differing phenotypes has always been of interest to people.ravenousaddict.deviantart.com

Introduction The proposal that a gene is responsible for the production of a specific protein was first put forward by Archibald Garrod in 1909. This idea, together with work on the inheritance of eye colour in Drosophila, led biologists to investigate the importance of genes in enzyme production.www.dec.ufcg.edu.br

Beadle and TatumGeorge Beadle and Edward Tatum (1941) worked on mutants of the fungus Neurospora crassa (a mould), leading to their groundbreaking discovery that genes provide the instructions for making proteins.sandwalk.blogspot.com

Beadle and TatumThey put forward the hypothesis that one gene controls the production of one enzyme. This was based on observations made in Beadles earlier experiments on fruit flieshe found that if fruit flies with normal eye colour were exposed to X-rays, their offspring would show a change in eye colour. He hypothesised that this occurred as a result of a defective enzyme for the eye pigment.news.sciencemag.org

Beadle and TatumSince evidence was needed to support this hypothesis, Beadle and Tatum designed and carried out an experiment to attempt to mutate genes of the mould Neurospora crassa, the enzyme functioning of which they could test fairly simply. www.dnaftb.org

Beadle and TatumExperimental evidence led them to propose a hypothesis that genes affect enzyme productionthe details of this were later modified as the understanding of the relationship between genes and proteins advanced.www.readcube.com

Beadle and Tatums Experiment It is important to remember that at the time that Beadle and Tatum began their research, biologists were still not sure of the chemical nature of the heredity materialthere was still ongoing debate as to whether it would prove to be protein or DNA. This is why their discovery was such a major breakthrough.pinterest.com

ActivityVisit website and do activity together (10-15min):http://www.dnalc.org/resources/nobel/beadle_tatum.html

pinterest.comBeadle and Tatums Experiment Beadle and Tatums one geneone enzyme hypothesis changed to the one geneone protein hypothesis, once it was demonstrated that there are other proteins besides enzymes that are encoded by genes.sandwalk.blogspot.com

Beadle and Tatums Experiment After the discovery by biologists that one gene is not necessarily responsible for the structure of an entire protein, but for each polypeptide chain making up that protein, the current one geneone polypeptide hypothesis was adopted. This is the currently accepted theory and has stood up to rigorous testing, holding true for all predictions so far.users.rcn.com

Beadle and Tatums Experiment George Beadle and Edward Tatums discovery won them the Nobel Prize for Physiology or Medicine in 1958.www.readcube.com -

Activity/Homework-Students to visit site and go through experiment again on their own.http://www.dnalc.org/resources/nobel/beadle_tatum.html

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