CSB325 Lecture 7 Review Notes

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University of Toronto St. George
Cell and Systems Biology
David Lovejoy

CSB325 Lecture 7 – Feeding, Digestion, Appetite - All key hormones associated with digestion utilize GPCR, with the exception of insulin which uses a kinase receptor system - In digestive endocrinology, a number of peptides are structurally related and are therefore grouped in families - The degree of relatedness indicates an evolutionary relationship among these families - Similar hormones may be utilized by a variety of species to carry out similar functions - However, these hormones and their genes may vary in structure due to changes that occur during evolution - Consequently, hormones and their genes are classified as homologues, orthologues, or paralogues - The number of hormones in an organism is directly related to the amount of genetic material present - An increase in the genetic complexity is determined by the number of gene and genomic duplications - Early vertebrates appear to have two major genome duplication events - Later genomic duplication events occurred in cartilaginous fish, amphibians and ray finned fishes - Orthologues  gene (hormone) changes as a function of species divergence Mammals (urocortin) Lobe finned fishes Amphibians (sauvagine) Cartilaginous fish Holosteans (urotensin-I) Ray finned fishes Teleosts (urotensin-I) - Paralogues  gene (hormone) changes as a function of gene or genomic duplication o Genomic duplication can confer a selective advantage to the organism o If a gene is essential for survival, then mutation of that gene could reduce the survivability of that organism o If the gene or genome duplicates, then one gene is free to mutate without significantly affecting the survivability of the organism o Over time, the second gene takes on a modified physiological role o E.g., calcitonin and PTH o E.g., GHRH and PACAP o E.g., CRF and UCN Corticotropin releasing factor (CRF) CRF/UCN like Urocortin (UCN) CRF/UCN/UCN-II/UCN-III like UCN-II UCN-II/UCN-III like UCN-III - Homologues  genes (hormones) that look structurally similar  genetic or s
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