What would you do to determine whether a black horse is pure

What would you do to determine whether a black horse is pure bred for color? (Black is dominant; gray is recessive).

Solution

whenever we have a dominant character organism and we don\'t know whether its homozygous or heterozygous, we do a test cross,

In a test cross, we cross the unknown genotyped organism with a homozygous recessive individual.

depending on the results of the cross that we get, we can conclude if the unknown organism is heterozygous or pure bred.

an example would be :

case 1 : if the horse is heterozygous, then :

the ratio of black and grey offsprings would be 1:1

whereas if the horse is pure bred, then :

all of the offsprings would be black in color.

therefore by using a test cross we can find out if an organism is homozygous dominant or heterozygous.

gametes	B	b
b	Bb	bb
b	Bb	bb