1. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk X Linked Inheritance Transmission patterns

2. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk Fig. 1.10 ©Scion Publishing Ltd Pedigree of Martin Daviess family. Assuming this is X-linked muscular dystrophy, the women marked with dots are obligate carriers of the disease gene – that is, they must be carriers because they have both parents and offspring who are affected or carriers.

3. © 2009 NHS National Genetics Education and Development CentreGenetics and Genomics for Healthcare www.geneticseducation.nhs.uk Fig. 1.16 ©Scion Publishing Ltd Pedigree of an X-linked dominant condition. Although heterozygous females are affected, such conditions are usually milder and more variable in females than in males.

4. © 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

5. © 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

6. © 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