Year 10, Pathway C 2012 New Generations

Outcomes Calculate genotypic/phenotypic ratio of sex-linked inheritance using punnet squares and pedigree charts

Sex-linked inheritance Certain diseases appear on the X sex chromosome only. These are called sex linked diseases Colour blindness Haemophilia Duchenne muscular dystrophy X Y

Sex-linked inheritance Subscripts are used to indicate chromosomes which carry the disease: X – Normal chromosome XC - Chromosome with disease XX – Normal female X XC – Carrier female XC XC – Affected female XY – Clear male XCY – Affected male

What are the chances? If an affected male has a child with a normal female, what are the chances the child will be affected?

What are the chances? If an affected male has a child with a normal female, what are the chances the child will be affected? No child will be affected. However, any girls will be carriers.

What are the chances If an affected male has a child with a carrier female, what are the chances the child will be affected?

What are the chances If an affected male has a child with a carrier female, what are the chances the child will be affected? 2 out of every 4 children will be affected. Half the girls will be carriers.

Sex linked pedigree charts Male with disease Male without disease Female with disease Female without disease. (could be a carrier)

Sex linked pedigree charts What are the genotypes of parents 1 and 2? 1 2

Sex linked pedigree charts What are the genotypes of parents 1 and 2? 1 2

Outcomes Calculate genotypic/phenotypic ratio of sex-linked inheritance using punnet squares and pedigree charts