Mutant flies helped us discover intragenic recombination

A reversion to wild-type associated with crossing-over in Drosophila melanogaster. Oliver CP. Proc Natl Acad Sci U S A. 1940 Jul 15;26(7):452-4. doi: 10.1073/pnas.26.7.452. OTHER VIDEOS YOU MIGHT LIKE: • How the creation of recombinant DNA shaped the future of gene therapy -    • How the creation of recombinant DNA shaped...   • Revealing the secrets of evolution from genome sequencing of peach -    • Revealing the secrets of evolution from ge...   • Foreign life in our cells?! Find out in the Marvellous Mystery of Mitochondria! -    • Foreign life in our cells?! Find out in th...   Recombination is an amazing process that happens in many different organisms. But how was it discovered? Initially, scientists believed that genes were individual blocks organised together much like beads on a string. This theory lay in place for upwards of 30 years since its introduction in the 1910s. However, Clarence Paul Oliver’s experiment was the first of many to question (and eventually debunk) this theory and lead us to our modern understanding of the gene. His ground-breaking experiment used mutations in Drosophila melanogaster, the common fruit fly, to observe how genes were passed down from one generation to the next. Fruit flies are amazing model organisms that many geneticists use because of their wide variety of observable traits and mutations, as well as their cheap costs and low maintenance. However, their well mapped genome is probably one of their most important strengths, which allowed Oliver to easily identify where crossing over occurs within the chromosome by studying mutations in the lozenge locus. The results of Oliver’s experiment were the first of many experiments that could not be supported by the bead-on-a-string theory. Many other scientists such as Lewis, Green and Green all contributed to the discovery of crossing over within genes with their own experiments. Lewis observed a similar result in that some Drosophila reverted back to wild-type when testing star eye alleles. Green and Green created an initial map of the lozenge locus using Oliver’s and Lewis’s foundational work. Benzer was the first to describe what we now know as nucleotides and what we now understand to be as the smallest hereditary unit. This discovery by Benzer finally explains the observations in Oliver’s experiment and debunked the bead-on-a-string theory. However, without Oliver’s foundational work, it is possible that we may not have discovered the nucleotide as the minimal recombining unit of the gene for many years to come. Creator: Annabelle Mouat References: Benzer S. Fine structure of a genetic region in bacteriophage. Proc Natl Acad Sci U S A. 1955;41(6):344-354. Green MM, Green KC. Crossing-over between alleles at the lozenge locus in Drosophila melanogaster. Proc Natl Acad Sci U S A. 1949;35(10):586-591. Jennings BH. Drosophila – a versatile model in biology and medicine. Mater Today. 2011;14(5):190-195. Lewis EB. Another case of unequal crossing-over in Drosophila melanogaster. Proc Natl Acad Sci U S A. 1941;27(1):31-35. Lewis EB. The relation of repeats to position effect in Drosophila melanogaster. Genetics. 1945;30(2):137-166. Lewis EB. C. B. Bridges' repeat hypothesis and the nature of the gene. Genetics. 2003;164(2):427-431. Oliver CP. A reversion to wild-type associated with crossing-over in Drosophila melanogaster. Proc Natl Acad Sci U S A. 1940 Jul 15;26(7):452-4. Stapley J, Feulner PGD, Johnston SE, Santure AW, Smadja CM. Recombination: the good, the bad and the variable. Philos Trans R Soc Lond B Biol Sci. 2017;372(1736):20170279.