Download Gene interaction - epistasis

Gene interaction – Epistasis
prepared by Dr. Paul Kusolwa
• Complementary interaction = 9:7
• Dominant epistasis = 12: 3: 1 A >B
• Duplicate dominant epistasis 15:1 A and B gives
new phenotype
• Dominant Suppression 13:3 A suppress B locus
at dominant state
Fruit colors in sweet pepper
F2
9 Red
3 Yellow
3 Brown
1 Green
Dominant epistasis – Solid fruit color in summer squash
•Modified Dihybrid ratio for fruit color
•12:3:1 ratio
Alleles W and w for color expression
W = white fruits (weak coloration), w
recessive = for colored fruits
At another locus Y for yellow fruits
Y is dominant to y = Yellow fruits
y – recessive = green fruits
Dominant Epistasis - W
negates the dominance
of Y for color expression
Both w and y when present in recessive
conditions both gives green fruit color
Zucchini – summer squash
•selection against the dominant W
alleles
Fruit shapes in squash
Di locus
Dominant to spherical or pyriform
Duplicate genes with cumulative effects
When Di is present together with Spherical S
locus Di is dominant = Disc fruits
When Di present with recessive s = spherical
fruits
When didi/ss = long or pyriform fruits
9 Discs
Di_S_
Modified Ratio = 9: 6: 1
1 Pyriform di/s
6 Spherical = Di/s & di/S_
Complementary interaction
Pathway involving two genes
Wt = warty fruits Dominant to
non warty wt
Hr = hard rind
hr = intermediate texture
9:7
B_
Hr_
Wt_
Y_
Bicolor fruits = locus B pleiotropic for
fruits and leaves
For yellow and green color patches BB
or Bb
Extent of yellow or green
dosage of another incompletely
dominant, additive to modifier
genes. Ep1 and Ep 2
Ep1 and Ep2 alleles are involved
in enlarging the yellow patches
Genotypes
Bb with a dosage of 0 to 1 Ep
alleles = bicolor green and
yellow fruits
Dosage of 2-4 dominant alleles
Ep extends the yellow
coloration
Genotypes
9 B_Ep_
3 B_epep
3 bbEp_
1bbepep
Extended yellow
Yellow narrow
Green extended
green
12:4
Three or more genes interactions in ornamental gourds
Gb = green bands; gb for no bands
Gr/G = green rind (gr/g buff skin)
L-2 = color intensity (yellow /orange)
Gr
Gb
L-2
Ep-1/2
B_ bicolor
L-2 intensity
Pro ovary
momo-1
Complementary recessive for
loss of green fruit color
before maturity
mo-1 Mature orange color
mo-2 Mature orange
MoMo -1