Download TTRR

Linkage (allelic
interactions) & Epistasis
(non-allelic interactions)
F1
TtRr
TtRr
Ttrr
Tall/Resist
Tall/Susc
x
Recessive
ttrr
ttRr
Short/Resist
ttrr
Short/Susc
Test Cross
Phenotype
Genotype
Frequency
Tall and Resistant
TtRr
79
Short and Resistant
ttRr
18
Tall and Susceptible
Ttrr
22
Short and Susceptible
ttrr
81
Linkage
Recombination
Number of Recombinants
Number of Observations
18+22 = 0.2
200
F1
TtRr
Self
TR
0.4
Tr
0.1
tR
0.1
tr
0.4
Linkage
Gametes from
female parent
Gametes from male parent
TR-0.4
Tr-0.1
tR-0.1
tr-0.4
TR – 0.4
TTRR
0.16
TTRr
0.04
TtRR
0.04
TtRr
0.16
Tr – 0.1
TTRr
0.04
TtRR
0.04
TtRr
0.16
TTrr
0.01
TtRr
0.01
Ttrr
0.04
TtRr
0.01
ttRR
0.01
ttRr
0.04
Ttrr
0.04
ttRr
0.04
ttrr
0.16
tR – 0.1
tr – 0.4
16 TTRR:8 TTRr:1 TTrr:8 TtRR:34 TtRr:8 Ttrr:1 ttRR:8 ttRr:16 ttrr
Linkage
F2 Genotype
50% Recom.
20% Recom.
TTRR
TTRr
TTrr
TtRR
TtRr
Ttrr
ttRR
ttRr
ttrr
6
13
6
12
26
12
6
13
6
16
8
1
8
34
8
1
8
16
Linkage
F2 Phenotype
50% Rec.
20% Rec.
T_R_
T_rr
ttR_
ttrr
56
19
19
6
66
9
9
16
Linkage
Independent
Assortment
¼ AB
Coupling
Linkage
> ¼ AB
Repulsion
Linkage
< ¼ AB
¼ Ab
< ¼ Ab
> ¼ Ab
¼ Ab
< ¼ aB
> ¼ aB
¼ ab
> ¼ ab
< ¼ ab
F2
TTRR
TTRr
TTrr
TtRR
TtRr
Ttrr
ttRR
ttRr
ttrr
160
80
10
80
340
80
10
80
160
Total
F3
F2
TTRR
TTRr
TTrr
TtRR
TtRr
Ttrr
ttRR
ttRr
ttrr
160
80
10
80
340
80
10
80
160
TTRR
160
20
-
20
54
-
-
-
-
254
TTRr
-
40
-
-
27
-
-
-
-
67
TTrr
-
20
10
-
4
20
-
-
-
54
TtRR
-
-
-
40
27
-
-
-
-
67
TtRr
-
-
-
-
116
-
-
-
-
116
Ttrr
-
-
-
-
27
40
-
-
-
67
ttRR
-
-
-
20
4
-
10
20
-
54
ttRr
-
-
-
-
27
-
-
40
-
67
Ttrr
-
-
-
-
54
20
-
20
160
254
Total
Linkage
F3 Genotype
TTRR
TTRr
TTrr
TtRR
TtRr
Ttrr
ttRR
ttRr
ttrr
50% Rec.
141
94
141
94
62
94
141
94
141
20% Rec.
254
67
54
67
116
67
54
67
254
Linkage
F3 Phenotype
50% Rec.
20% Rec.
T_R_
T_rr
ttR_
ttrr
391
234
234
141
504
121
121
254
Undesirable Linkage
Increased selfing or
crossing before
selection
Three gene test cross
AABBCC x aabbcc
AaBbCc
1
2
3
Three gene test cross
AABBCC x aabbcc
AaBbCc x aabbcc
1
2
3
Three gene test cross
Phenotype
Observed
Expected
A_B_C_
aabbcc
aaB_C_
A_bbcc
A_bbC_
aaB_cc
A_B_c
aabbC_
Total
500
510
50
55
35
38
4
3
1195
149.4
149.4
149.4
149.4
149.4
149.4
149.4
149.4
1195
Three gene test cross
Acb
aCB
ACb
acB
AcB
aCb
A
C
B
a
c
b
A
C
B
a
c
b
A
C
B
a
c
b
55
50
35
38
4
3
Three gene test cross
A – B locus
A_B_
500+4 = 504
aabb
510+3 = 513
aaB_
50 + 38 = 88
A_bb
55 + 35 = 90
Parent types
Aa
Cc
Bb
Recombinants
% Recombination = 178/1195 x 100 = 14.9%
Three gene test cross
A – C locus
A_C_
500+35 = 535
Aacc
510+38 = 548
aaC_
50 + 3 = 53
A_cc
55 + 4 = 59
Parent types
Aa
Cc
Bb
Recombinants
% Recombination = 112/1195 x 100 = 9.4%
Three gene test cross
B - C locus
B_C_
500+50 = 550
Bbcc
510+55 = 565
bbC_
35 + 3 = 38
B_cc
38 + 4 = 42
Parent types
Aa
Cc
Bb
Recombinants
% Recombination = 80/1195 x 100 = 6.7%
Three gene test cross
A
A
14.9 m
9.4 m
C
B
6.7 m
B
Three gene test cross
A - B locus
Aa
Cc
Bb
NonRecombinant
types
A_B_C_
500
aabbcc
510
Recombination
events
aaB_
50+39 = 88
A_bb
55+35 = 90
Double cross overs
2 x (3+4) = 14
% Recombination = 192/1195 x 100 = 16.1%
Three gene test cross
A
A
16.1 m
9.4 m
C
B
6.7 m
cM = [-Ln(1-2R)] x 50
B
Three gene test cross
A
A
16.1 m
9.4 m
C
B
6.7 m
B
cM = [-Ln(1-2R)] x 50
A
A
17.7 cM
10.5 cM
C
s.e. = [R/(1-R)]/n
B
7.0 cM
B
Epistasis
Non-allelic Interactions
Epistasis
Parent 1
White flower
x
Parent 2
White flower
F1- 100% Blue Flower
Hairbells
Epistasis
Parent 1
White flower
Parent 2
White flower
x
F1- 100% Blue Flower
9 Blue
:
7 White
Epistasis
Parent 1
White flower
w1w1W2W2
Parent 2
White flower
W1W1w2w2
x
F1- 100% Blue Flower
W1w1W2w2
Blue flower
W1_W2_
9 Blue
:
7 White
White flower
3-W1_w2w2
3-w1w1W2_
1-w1w1w2w2
Epistasis
Precursor
Enzyme
Gene W_
substrate
Enzyme
Gene M_
Blue
Epistasis
Parent 1
White flower
x
Parent 2
Magenta flower
F1- 100% Blue Flower
Blue Eyed Mary (Collinsia parviflora)
Epistasis
Parent 1
White flower
Parent 2
Magenta flower
x
F1- 100% Blue Flower
9 Blue
:
3 Magenta
:
4 White
Epistasis
Colorless
Magenta
Gene W_
Blue
Gene M_
Epistasis
Colorless
Magenta
Gene W_
Parent 1
White flower
wwMM
Blue
Gene M_
x
Parent 2
Magnolia flower
WWmm
Epistasis
Parent 1
White flower
wwMM
Parent 2
Magnolia flower
WWmm
x
F1- 100% Blue Flower
WwMm
9 Blue
W_M_
:
3 Magnolia
W_mm
:
4 White
wwM_ & wwmm
F2 phenotype
A_B_ A_bb aaB_
aabb
Genetic explanation
9
3
3
1
Complete dominance: A dominant to a, B
dominant to b.
9
3
4
0
Recessive epistasis: aa epistatic to B and b.
12
0
3
1
Dominant epistasis: A epistatic to B or b.
0
Dominant & recessive epistasis: A epistatic to
B and b; bb epistatic to A and a; A_ and bb
identical phenotypes
0
Duplicate recessive epistasis: aa epistasis to B
and b; bb epistatic to A and aa
1
Duplicate dominant epistasis: A epistasis to B
and bb; B epistasis to A and aa.
13
9
15
0
0
0
3
7
0
Autotetraploid Segregation
& Chi-square