1. Eye Color

2. Scarlet x Brown Cross

3. The phenotype of one gene is influenced by the genotype of another
Epistasis
The phenotype of one gene is influenced by the genotype of another
Eye color in Drosophila melanogaster (fruit flies) shows epistasis
in this case both brown and scarlet flies are homozygous recessive
the F1 wild type flies will be heterozygous for brown and scarlet P0 F1 F2
brown x scarlet
wildtype
Wild type brown scarlet white
heterozygotes can give both individual mutant phenotypes as well as a
new 'white' phenotype (double homozygous recessive mutants)

4. Scarlet Vs Brown Scarlet Phenotype: ssBB; ssBb
Brown Phenotype: SSbb; Ssbb
Wild Type: SsBb; SsBB; SSBB;
White: ssbb

5. Scarlet Vs Brown Cross: ssBB x SSbb
All offspring will be SsBb = Wild
This is your F1 offspring – of the Scarlet and wild cross –
they “should” all look “WILD”
Then you cross the F1 - Dihybrids

6. Cross: SsBb x SsBb (“wild”)
SB Sb sB sb SB
SSBB
SSBb
SsBB
SsBb
SSbb
Ssbb
ssBb
ssbb Sb sB sb

7. Gene Interaction Type of Epistasis:
“ss” or (st,st) = no brown produced
“bb” or (bw,bw) = no scarlet produced
“ssbb” or (st,st,bw,bw) = no color produced at all