Trihybrid cross

AAPD2BB

• The mating of two individuals, organisms, or strains that have different gene pairs that determine three specific traits or in which three particular characteristics or gene loci are being followed.

Example:

23 = 8 * 8 = 64MEANING:• The fork line method can be used by

figuring the occurrence of each gene or set of genes to be found in the gamete, and then multiply them together.

• This can be multiplied by figuring each trait or combination of traits separate for both the male and female, or each gene individually regardless of sex.

P1: WWGG * ww gg

F1: Ww Gg * Ww Gg

F2: Ww * Ww Gg * GgWW Ww Ww ww GG Gg Gg gg

Phenotypes:

¾ W ¾ G = 9/16 WG

¼ g = 3/16 Wg

¼ w ¾ G = 3/16 wG

¼ g = 1/16 wg

Phenotypic ratio:9:3:3:1

Genotypes: ¼ GG = 1/16 WW GG

¼ WW 2/4 Gg = 2/16 WW Gg

¼ gg = 1/16 WW gg

¼ GG = 3/16 Ww GG

2/4 Ww 2/4 Gg = 4/16 Ww Gg

¼ g = 2/16 Ww gg

¼ GG = 1/16 ww GG

¼ ww 2/4 Gg = 2/16 ww Gg

¼ gg = 1/16 ww gg

genotypic ratio: 1:2:1:2:4:2:1:2:1