How could we know whether a trait is autosomal or sex linked by studying a pedigree?
they are distinguished through notation - a sex-linked pedigree will have mostly affected males, the female carriers are typically designated as a half shaded circle.
Autosomal traits can also be identified when a female offspring shows a recessive trait and the father is not affected & if an affected mother has a non-affected son.
The discussion below considers only recessive traits.
- In a pedigree displaying autosomal trait, affected individuals are of both sex: that is both male and female individuals could be affected in 1:1 ratio.
- In a pedigree displaying sex linked trait, an overwhelming number of males will be affected.
- In case of autosomal trait, both male and female individuals could be carriers.
- In case of sex linked trait, carriers are always female individuals, never male.
- An autosomal trait generally appears to affect individuals in every generation.
- A sex linked trait shows 'criss cross inheritance'.