Mon Spr W4 - Genome Evolution - Gene duplication (Lec4) Describe how duplication generates families of genes that have related functions homologous genes - genes that share a common evolutionary ancestor orthologous genes - homologous genes located in the genomes of different organisms paralogous genes - two or more homologous genes located in the same genome pseudogene - an inactivated & non-functional copy of a gene Gene Family - multiple genes that have arisen from duplication of a single original gene, genes often have similar functions Gene Cluster - Group of 2+ genes found within organisms DNA sequence, encode polypeptides that have similar functions and are few thousand base pairs from each other, are from same gene family Olfactory bult Bone Nasal epithelium Olfactory receplot Calle Mitral- coll Glomerulus 4. The signal are transmitted to Higher regions of the brain 3. The signals arn rdayed in glomeruli 1991 nobel prize winning paper described large family of odour receptor genes (olfactory receptor genes) 2. Olfactory receptor cells are activated and send electric signals 1. Odorants bind to receptors Makes up 3% of genes in human genome Air with odorant molecules `Odorant receplof 906 gene sequences code for o.r genes, with each receptor spec to one gene Mixture of the receptors gives us a sense of smell!
400 300 200 MYA a Human Chimpanzee Macaque Mouse Rat Dog Cow Opossum 1198 Platypus Chicken Xenopus Fugu Zebrafish 100 0 OR 0 1,000 2,000 388 (414) 399 (414) 326 (280) (328) 1063 1259 (508) 822 (278) 1152 (977) (294) 348 (370) 300 (133) 1024 86 (39) 155 (21) (614) Figure shows diversity and evolutionary differences between organisms (red -> func genes/ blue -> pseudogenes + ancient non-functional genes) 80% human olfactory genes appear in clusters ( may be evidence for evolutionary selection as it takes a long amount of time for gene duplication and gene families to form Zebra fish + Fugu have same gene families but only have small no. genes in common Duplication of genes must have played sig. Impact on human genome evolution
Summarise with some examples why gene families are important components of most genomes 3 outcomes gene duplication Gene duplication 1) Gene stays similaire 2) One copy of duplicated gene degrades 3) One copy acquires new function Selective pressure on both genes Selective pressure on just one of the genes Genes stay similar Figuw 18-2 Genames 340 Garland Science 2007) One copy degrades One copy acquires a new function Ancestral globin ~800 MYr -500 MYr ~550 MYr ~450 MYr Globin gene is a superfamily of genes that exists due to duplication It consists of very few genes but ancient (800MYa) - this lineage has been predicted by comparing human genome to other organism's ~200 MYr € G, Ay ~150 MYr a and B globins code for proteins that make up haemoglobin 8 B Neuroglobin Cytoglobin Myoglobin Figure 18-8 Genomes 3 (0 Garland Science 2007) Therian ancestor a-Globins B-Globins Marsupials Myoglobin - O2 binding in muscles Neuroglobin - O2 binding