What is an example probability in genetics practice problem?

1 Answer


Example: Suppose a mother and father is both heterozygous for the characteristics of brown eyes and brown hair, ie they have brown eyes and brown hair but carry the recessive gene for blond hair and blue eyes.
Calculate the probability that they would produce a blue-eyed, blond-haired boy as a child.


Since 1 gene from each parent is given for a character trait, together with the sex determination being carried on the gonosome (23rd chromosome), there is a 1 in 4 chance of each characteristic (blue eyes and blond hair) and a 1 in 2 chance of a boy as opposed to a girl.
Therefore the overall combined probability may be found by using the multiplication principle as follows :
#1/4x1/4x1/2 = 1/32# ie a 0,03125 probability or a 3,125% chance of it happening.