In mice, the ability to run normally is a dominant trait. Mice with this trait a
ID: 198208 • Letter: I
Question
In mice, the ability to run normally is a dominant trait. Mice with this trait are called “running mice” (R). The recessive trait causes mice to run in circles only. Mice with this trait are called “waltzing mice” (r)
Hair color is also inherited in mice.Black hair (B) is dominant over brown hair (b).
A) Cross a heterozygous running mouse with a homozygous running mouse.
i. What are the parentgenotypes? __________ x ____________
ii. Draw the punnett square
iii. What is the genotype ratio?
iv. What is the phenotype ratio?
.
B) Cross a homozygous brown mouse with a homozygous brown mouse.
i. What are the parent genotypes? __________ x ____________
ii. Draw the punnett square
iii.What is the genotype ratio?
iv. What is the phenotype ratio?
C) Cross a homozygous waltzing mouse with a heterozygous running mouse.
i. What are the parent genotypes? __________ x ____________
ii. Draw the punnett square
iii. What is the genotype ratio?
iv. What is the phenotype ratio?
D). Cross a homozygous waltzing, heterozygous blackmouse with a homozygous waltzing, heterozygous black mouse.
i. What are the parent genotypes? __________________ x ___________________
ii. Draw the punnett square (4x4 square)
iii. What is the phenotype ratio?
E). Cross a homozygous running, heterozygous blackmouse with a waltzing, brown mouse.
i.What are the parentgenotypes? __________________ x ___________________
ii. Draw the punnett square (4x4 square)
iii. What is the phenotype ratio?
Explanation / Answer
Rr, RR, RR, Rr
So all will be running mice with a genotypic ratio of 1:1 or Rr and RR
Phenotypic ratio = 4:0
2. B)
bb xbb
bb,bb,bb,bb
100% brown mice.
Genotypic and phenotypic ratio will be 4:0
C)
rr X Rr
Rr, Rr, rr, rr
Phenotypic ratio = 1:1 of walting to running mice
Genotypic ratio 1:1 of walting to running mice
D).
rrBb X rrBb
F1 rB, rb
rb
rB
rB
rb
rb
rrbb
rrBb
rrBb
rrbb
rB
rrBb
rrBB
rrBB
rrBb
rB
rrBb
rrBB
rrBB
rrBb
rb
rrbb
rrBb
rrBb
rrbb
Genotypic ratio: 4rrbb, 8rrBb, 4 rrBB (1:2:1)
Phenotypic ratio: 4 walting brown mice: 12 walting black mice
1:3
E).
RB, Rb X rb Punette square
rb
rb
rb
rb
RB
RrBb
RrBb
RrBb
RrBb
RB
RRBb
RRBb
RRBb
RRBb
Rb
Rrbb
Rrbb
Rrbb
Rrbb
Rb
Rrbb
Rrbb
Rrbb
Rrbb
Genotypic ratio: 8 RrBb : 8Rrbb (1:1) Running black: running brown
Phenotypic ratio: 1:1 Running black: running brown
rb
rB
rB
rb
rb
rrbb
rrBb
rrBb
rrbb
rB
rrBb
rrBB
rrBB
rrBb
rB
rrBb
rrBB
rrBB
rrBb
rb
rrbb
rrBb
rrBb
rrbb
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