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Appetite regulating genes-jwu gu2z,pa5l kz f6.om+rt; expressed ir /rdlf rq 2g5nf:j,2rn the brain are understood to have an important role in feeding behaviour and the study of this is important in order to understand the underlying causes of feeding disorders. However, other areas, outside the : fdjqf2grrr2l/n r5,brain, such as the gastrointestinal tract, are receiving attention for their potential influence in the regulation of appetite.
In a study, scientists investigated the expression of appetite-regulating genes in the gut, using zebrafish (Danio rerio) as a model organism.
In their first experiment, a variety of feeding conditions were applied to wild type zebrafish and the expression of different genes, known to have a role in appetite regulation, were measured.
1.Identify the gene and feeding condition which show the greatest difference in relative fold change in expression compared to the control.
2.Describe the effect of feeding conditions on the expression of the galr2a gene.
3.Calculate the increase, as a percentage, in the relative fold change in expression between the control feeding condition and the fasted feeding condition for the gene cnr1. The percentage is %
4.State the name of the gene which had the greatest increase in expression when zebrafish were fed every 2 hours.The name of the gene is .
In a second experiment, scientists used a zebrafish mutant, which, unlike the wild type, had impaired leptin receptors, due to a mutant gene lepr. The same feeding conditions were then applied and the expression of the same genes were measured.
5.1.Compare and contrast the effect of feeding conditions on the expression of the apln gene in wild type and mutant zebrafish.
5.2.State which feeding condition, other than the control, had the most similar results for wild-type and lepr-mutant zebrafish for the gene scg2a.
A final experiment was conducted to test the effect of a variety of known appetite suppressing agents on the feeding volume of zebrafish, as a precursor to studying their effect on gene expression.
In the experiment, paramecia were fluorescently labelled and fed to zebrafish, with transparent body cavities, which were treated using an appetite suppressing agent. Using a 96-well microplate reader, scientists were able to measure the intensity of fluorescence in zebrafish as a measure of the volume of paramecia they consumed. The experiment and its results are outlined below.
6.1.State the name of the agent which, at a concentration of 3.3µM, resulted in zebrafish having the poorest appetite.
resulted in the zebrafish having the poorest appetite.
6.2.Suggest why there are no results for Mazindol at a concentration of 10µM.
7.Approximately 70% of the coding genes of zebrafish are related to humans, and about 84% of human genes associated with disease are related to zebrafish. Evaluate the use of zebrafish in the study of obesity in humans.
