Happy (H), Cheddar (D), and Yellow (E). Mutant phenotypes seen for these traits
ID: 224155 • Letter: H
Question
Happy (H), Cheddar (D), and Yellow (E). Mutant phenotypes seen for these traits are expressionless (h), pretzel (d), and brown (e). Data from a three point testcross are shown below.
Phenotype
Number of Progeny
Normal
102
Expressionless
10
Pretzel
804
Brown
94
Expressionless, Pretzel
102
Expressionless, Brown
790
Pretzel, Brown
8
Expressionless, Pretzel, Brown
90
What are the genotypes of the testcross?
x
What is the order of the three genes h, d, and e?
Create a genetic map (including distances) that represents the relationship of the three loci above? (Show all your Work)
Phenotype
Number of Progeny
Normal
102
Expressionless
10
Pretzel
804
Brown
94
Expressionless, Pretzel
102
Expressionless, Brown
790
Pretzel, Brown
8
Expressionless, Pretzel, Brown
90
Explanation / Answer
Answer:
1). Genotype of test cross:
HEd/ heD x hed/hed
2). Orfer of genes is h –-----7.13 m.u.-----e-------7 m.u.------d
Explanation:
Shorthand
Number of progeny
HDE
102
hDE
10
HdE
804
HDe
94
hdE
102
hDe
790
Hde
8
hde
90
Total 3000
Parental combinations are more so, the parental combinations are HdE & hDe
1. If single cross over (SCO) occurs between H & d and h &D
Normal order= H --------d & h ----- D
After cross over= H ----- D & h------d
H ----- D recombinants are 102+94= 196
h------d recombinants are 102+90=194
Total recombinants = 390
RF = (390/3000.)*100 =13%
2. If single cross over (SCO) occurs between d & E and D & e
Normal order= d --------- E & D --------- e
After cross over= d --------- e & D ------ E
d --------- e recombinants are 8+90=98
D ------ E recombinants are 10+102=112
Total recombinants = 210
RF = (210/3000)*100 = 7%
3. If single cross over (SCO) occurs between H & E and h & e
Normal order= H --------- E & h------e
After cross over= H --------- e & h---------E
H --------- e recombinants are 94+8 = 102
h--------- E recombinants are 102+10= 112
Total recombinants = 214
RF = (214/3000)*100 = 7.13%
% RF = Map unit distance
The order of gene is -----
h –-----7.13 m.u.-----e-------7 m.u.------d
Shorthand
Number of progeny
HDE
102
hDE
10
HdE
804
HDe
94
hdE
102
hDe
790
Hde
8
hde
90
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