1. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk Segregation of Alleles in X-linked inheritance This PowerPoint file contains a number of slides that may be useful for teaching of genetics concepts. You may use these slides and their contents for non-commercial educational purposes. This presentation includes: Segregation of alleles in X-linked inheritance DMD gene tracking in a family X chromosome tracking in a pedigree A pedigree example of an X-linked condition (SCID), showing the inheritance pattern.

2. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk Daughter Daughter (Carrier) Son Son (Affected) Parents Gametes At conception X-linked inheritance where the mother is a carrier Father Mother X Y X X (Carrier) (Unaffected)

3. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk X-chromosomes shown Therefore, Anne is not a carrier for Duchenne muscular dystrophy Tracking the inheritance of the gene causing Duchenne muscular dystrophy through the family

4. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk X chromosomes only are shown This pedigree pattern can be explained by deducing the inheritance of the maternal X chromosomes

5. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk or X chromosomes only are shown An equal chance of being a carrier or not

6. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk Fig. 7.12 ©Scion Publishing Ltd Pedigree of severe combined immunodeficiency in the Portillo family. The pattern shows that this is the X-linked form of this rare disease. The mother, grandmother and great- grandmother of the proband are obligate carriers. His sister, two aunts and female cousin are at risk of being carriers.