Punnett Squares for X-Linked Recessive Conditions
Punnett Squares for X-Linked Recessive Conditions
Description:
Below are sample Punnett squares for X-linked recessive conditions. The disease-causing mutation is denoted by the lower case letter a. The normal gene is denoted by the capital letter A. 
The Punnett square to the left is representative of possible reproductive outcomes should a female with an X-linked recessive mutation (a carrier) have children with a male who is clinically unaffected.
This couple has a 25% chance with each pregnancy of having a daughter who does not inherit the mutation (clinically unaffected), a 25% chance of having a daughter who inherits 1 copy of the mutation (a carrier), a 25% chance of having an unaffected son, and a 25% chance of having a son who inherits the mutation (clinically affected).
The Punnett square to the left is representative of possible reproductive outcomes should a female without an X-linked mutation have children with a male who is clinically affected with an X-linked recessive condition.
This couple has a 50% chance with each pregnancy of having a daughter who inherits the mutation (a carrier) and a 50% chance of having an unaffected son.
The Punnett square to the left is representative of possible reproductive outcomes should a female who is heterozygous for an X-linked recessive condition (a carrier) have children with a male who is clinically affected with the same condition.
This couple has a 25% chance to have a daughter who inherits 1 mutation (a carrier), a 25% chance to have a daughter who inherits 2 copies of the mutation (clinically affected), a 25% chance to have a son who inherits no mutation (unaffected), and a 25% chance to have a son who inherits 1 mutation (clinically affected).
