Teaching and Learning Genetics with Drosophila 5. Lessons from the Experiments with Curly and Bristle Mutant Stocks
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In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. “Classroom” is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science. H A Ranganath
Teaching and Learning Genetics with Drosophila 5. Lessons from the Experiments with Curly and Bristle Mutant Stocks∗
Centre for Human Genetics, Biotech Park Electronic City Phase I, Bangalore 560 100 Email: [email protected]
Even today, Drosophila remains as one of the potent eukaryotic systems to study different dimensions of inheritance. It provides a wide spectrum of genetic resource of mutants which are of immense help to look into the effects of different types of mutations as well the mechanisms underlying their maintenance. Experiments involving lethal mutations in Drosophila have helped us to realize a few more genetic lessons, and the same is discussed in this communication. Previously, I had introduced Drosophila as a potential model to conduct experiments, followed by a description of a few mutant stocks (Resonance, Vol.4, No.2, pp.48–52, 1999; Vol.4, No.9, 95–104, 1999). In subsequent articles, based on the patterns of inheritance of a few phenotypes, I had presented experiments to demonstrate the laws of segregation and independent assortment, autosomal and sex-linked inheritance, as well as the interaction of genes and linkage (Resonance, Vol.4, No.10, pp.78– 87, 1999; Resonance, Vol.5, No.7, pp.59–70, 2000.). Continuing
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Drosophila, the Queen of Genetics, is one of the most suitable model systems for laboratory exercises to teach and learn not only genetics but also many concepts in biology.
Vol.25, No.8, DOI: https://doi.org/10.1007/s12045-020-1028-5
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Figure 1. D. melanogaster: A with normal wings and normal bristles; B with curly wings and mutant bristles. Arrowhead and arrows point wings and bristles respectively. (Photo courtesy: Dr Gurudatta Baraka and Sri. Shreekrishna, Centre for Human Genetics).
along these lines, I describe an experiment here to understand how dominant lethal mutations can be maintained with the help of ‘Balancer Chromosomes’. Strains of D. melanogaster Used in the Experiment D. melanogaster, a dipteran insect has two pairs of wings. Of these, the front pair is attached to the second thoracic segment and is completely developed. These flattened wings, when not being involved in flight, are placed on the abdomen. The hind wings, on the third thoracic segment, are reduced and transformed into balancers or halteres. Long, tapering, pointed bristles are distributed all over the body of Drosophila (Figure 1A). The number and pattern of distribution of bristles are of taxonomic importance. In a mutant strain of D. melanogaster, the front pair of wings are curved upwards and forwards (Figure 1B), a phenotype referred
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