1. Trihybrid
cross
AAPD2BB

2. • The mating of two
individuals,
organisms, or strains
that have different
gene pairs that
determine three
specific traits or in
which three

3. Example:
23 = 8 * 8 = 64
MEANING:
• 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

4. P1: WWGG * ww gg
F1: Ww Gg * Ww Gg
F2: Ww * Ww Gg * Gg
WW Ww Ww ww GG Gg Gg gg
Phenotypes:
¾W 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

5. Genotypes:
¼ GG = 1/16 WW GG
¼ WW 2/ Gg = 2/ WW Gg
4 16
¼ gg = 1/16 WW gg
¼ GG = 3/16 Ww GG
2/4 Ww 2/ Gg = 4/ Ww Gg
4 16
¼ g = 2/16 Ww gg
¼ GG = 1/16 ww GG
¼ ww 2/ Gg = 2/ ww Gg
4 16
¼ gg = 1/16 ww gg
genotypic ratio: 1:2:1:2:4:2:1:2:1