•Homework #2 is due now •Bonus #1 is due 10/24 How does the organization of a genome affect its function? Map of human chromosome 20 Fig 13.13 http://www.ncbi.nlm.nih.gov/mapview/maps.cgi?ORG=human&CHR=X&MAPS=i deogr[Xpter:Xqter],genes[1.00:153692391.00] Some genes have several similar sequences within the genome: known as a gene family Hemoglobin (carries O2 in the blood) is comprised of a gene family in humans Different members of the hemoglobin gene family are expressed at different developmental stages Fig 19.17 Fetal Hb binds O2 more strongly than maternal Hb Pseudogenes have the structure of a gene, but are not expressed. Fig 19.18 Recently Mobilized Transposons in the Human and Chimpanzee Genomes (2006) Ryan E. Mills et al. The American Journal of Human Genetics 78: 671-679 and Which transposable elements are active in the human genome? (2007) Ryan E. Mills et al. Trends in Genetics 23: 183-191 Transposons: mobile DNA Transposons comprise much of human DNA From “Biology 7th ed.” by Campbell et al fig 19.14 Retrotransposons move via an RNA intermediate Fig 14.13 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Tbl 1 Recently Mobilized Transposons in the Human and Chimpanzee Genomes (2006) Ryan E. Mills et al. The American Journal of Human Genetics 78: 671-679 Humans and chimpanzees shared a common ancestor about 6 million years ago human QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. chimp Fig 3 Recently Mobilized Transposons in the Human and Chimpanzee Genomes (2006) Ryan E. Mills et al. The American Journal of Human Genetics 78: 671-679 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Tbl 2 Recently Mobilized Transposons in the Human and Chimpanzee Genomes (2006) Ryan E. Mills et al. The American Journal of Human Genetics 78: 671-679 Fig 1 Which transposable elements are active in the human genome? (2007) Ryan E. Mills et al. Trends in Genetics 23: 183-191 Conclusions: •Transposons may play a role in evolution •More abundant transposons in humans show “recent” transposon activity Conclusions: •Transposons may play a role in evolution •More abundant transposons in humans show “recent” transposon activity What affect do transposons have in humans? QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Fig 3 Recently Mobilized Transposons in the Human and Chimpanzee Genomes (2006) Ryan E. Mills et al. The American Journal of Human Genetics 78: 671-679 Does transposition cause disease? Tbl 1 Which transposable elements are active in the human genome? (2007) Ryan E. Mills et al. Trends in Genetics 23: 183-191 The coding capacity of L1 was not fully recognized until an active copy with intact ORFs ‘jumped’ into the factor VIII gene and caused hemophilia. Diseases caused by transposon insertion: •Duchenne muscular dystrophy •Coffin-Lowry syndrome •Fukuyama-type congenital muscular dystrophy (FCMD) •colon cancer •chronic granulomatous disease •X-linked dilated cardiomyopathy •familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism •neurofibromatosis type 1 Which transposons are mobile? Active human transposons have been estimated to generate about one new insertion per 10–100 live births Comparative genomics also has been used to identify recently mobilized transposons in genetically diverse humans. For example, over 600 recent transposon insertions were identified by examining DNA resequencing traces from 36 genetically diverse humans. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Which transposons are mobile? Tbl 1 Which transposable elements are active in the human genome? (2007) Ryan E. Mills et al. Trends in Genetics 23: 183-191 Conclusions: •Transposons may play a role in evolution •More abundant transposons in humans show “recent” transposon activity •Transposons are still active, and can cause mutations and disease.