1. Year 10, Pathway C
2012
New Generations

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

3. 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

4. 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

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

6. 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.

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

8. 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.

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

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

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

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