Punnett Square Practice KEY

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In rats, black color is dominant and white color is recessive.
Cross heterozygous black rat with a white rat

B=black b=white Bb x bb

B

b b P: 2/4 black,
2/4 white
1:1

b

Bb bb
Bb bb

G: 2/4 Bb
2/4 bb
1:1

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Can two white rats have a black offspring? Show the Punnett Square to confirm your answer

B=black
P: 4/4 white b=white 1:0 bb x bb  2 white rats
G: 4/4 bb b b
1:0

b b bb bb bb bb

NO, 2 white rats cannot have a black offspring.

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In humans the ability to taste a certain chemical is dominant.
Cross a homozygous taster with a heterozygous taster.

T=taster t=non-taster TT x Tt

T

T t G: 2/4 TT
2/4 Tt
1:1

T

TT TT
Tt Tt

P: 4/4 Tasters
1:0

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Albinism – lack of pigment – is caused by a recessive allele.
Cross an albino with a heterozygous, normally pigmented person (remember to choose your letters using the letter of the dominant allele)

N=normal pigment n=albino nn x Nn

n

N n n

Nn Nn nn nn

G: 2/4 Nn,
2/4 nn
1:1
P: 2/4 Normal
2/4 albino
1:1

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Cross a homozygous roller
(tongue, of course) with a heterozygous roller

R=roller r=non-roller RR x Rr

R

R r G: 2/4 RR
2/4 Rr
1:1

R

RR RR
Rr Rr

P: 4/4 Rollers
1:0

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Write the genotype of a heterozygous curly haired, homozygous albino, heterozygous tongue roller, homozygous taster.
Remember, you should have two alleles for each trait

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C=curly, c=straight
N=normal pigment, n=albino
R=roller, r=non-roller
T=taster, t=non-taster

 CcnnRrTT

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the phenotype for the following person using these letters for your alleles

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C = curly hair, c = straight hair
N = normal pigment, n = albino
R = roller, r = non-roller
T = taster, t = non-taster

ccNnrrTT

ccNnrrTT straight hair, normal-pigment, nontongue rolling, taster

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A spotted rabbit when crossed with a solid colored rabbit produced all spotted offspring. When these F1 rabbits were crossed within themselves, they produced thirtytwo spotted rabbits and ten solidcolored rabbits. Which