REVIEW: SIMPLE Punnett Squares

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Name: ____________________ Date: ____________________ Period: _____ Assignment #: ______
REVIEW: SIMPLE Punnett Squares
Use the following information to answer the following questions
TRAIT
Ear Shape
Widow’s Peak
Tongue Roll
DOMINANT ALLELE
Curved (E)
Widow’s Peak (W)
Can Roll (R)
RECESSIVE ALLELE
Pointed (e)
No Peak (w)
Can’t Roll (r)
Part I – For each description, write the GENOTYPE that person MUST have – there is ONLY 1 POSSIBLE
GENOTYPE for each description!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Homozygous dominant for curved ears: ____________
Homozygous recessive for pointed ears: ______________
Heterozygous for curved ears: _____________
Heterozygous for a widow’s peak: _______________
Homozygous recessive for tongue rolling: ______________
Homozygous dominant for tongue rolling: ________________
Heterozygous for tongue rolling: ________________
Homozygous recessive for widow’s peak: _______________
Homozygous dominant for widow’s peak: __________________
Pointed ears (there’s only 1 possible genotype!): _________________
No widow’s peak (there’s only 1 possible genotype!): _________________
Can’t tongue roll (there’s only 1 possible genotype!): _________________
Part II
1) Set up and fill in a Punnett Square representing the cross of a heterozygous curved ear with a
heterozygous curved ear.
Gentotype of heterozygous curved ear: __________
a) How many of the offspring would we expect to be Homozygous dominant? ____________ or ____%
b) How many of the offspring would we expect to be heterozygous dominant? ____________ or ____%
c) How many of the offspring would we expect to be homozygous recessive? _____________ or ____%
d) How many of the offspring would we expect to have curved ears? ___________________ or ____%
e) How many of the offspring would we expect to have pointed ears? _____________________ or ____%
f) What is the ratio of curved ears to pointed ears? ___to___
g) What is the ratio of homozygous dominant to heterozygous to homozygous recessive? ___ to ___ to ___
2 ) Set up and fill in a punnett square representing the cross of a homozygous tongue roller with a
heterozygous tongue roller.
Gentotype of homozygous tongue roller: __________
Genotype of heterozygous tongue roller: ___________
a) How many of the offspring would we expect to be homozygous dominant? ____________ or ____%
b) How many of the offspring would we expect to be heterozygous dominant? ____________ or ____%
c) How many of the offspring would we expect to be homozygous recessive? _____________ or ____%
d) How many of the offspring would we expect to be tongue rollers? ___________________ or ____%
e) How many of the offspring would we expect to be NON-tongue rollers? _____________________ or ____%
f) What is the ratio of tongue rollers to NON-tongue rollers? ___to___
g) What is the ratio of homozygous dominant to heterozygous to homozygous recessive? ___ to ___ to ___
3) Set up and fill in a punnett square representing the cross of homozygous widow’s peak with a homozygous
person with NO widow’s peak
Gentotype of homozygous widow’s peak: __________
Gentotype of homozygous NO widow’s peak: __________
a) How many of the offspring would we expect to be homozygous dominant? ____________ or ____%
b) How many of the offspring would we expect to be heterozygous dominant? ____________ or ____%
c) How many of the offspring would we expect to be homozygous recessive? _____________ or ____%
d) How many of the offspring would we expect to have a widow’s peak? ___________________ or ____%
e) How many of the offspring would we expect to NOT have a widow’s peak? _____________________ or ____%
f) What is the ratio of widow’s peak to no widow’s peak? ___to___
g) What is the ratio of homozygous dominant to heterozygous to homozygous recessive? ___ to ___ to ___
4) If we have two parents with curved ears (we don’t know if they are homozygous dominant or heterozygous) and
we want to figure out what their genotypes are, we can look at their babies! If we see that they have a child with
pointed ears, then what must be the parents’ genotypes?
- Remember: they can’t be cc, because they’re both CURVED  So they must be CC or Cc. Ask yourself:
 “If they are both CC, can they have a baby with pointed ears?”
Yes ___ No___
 “If they are CC and Cc, can they have a baby with pointed ears?” Yes ___ No___
 “If they are both Cc, can they have a baby with pointed ears?”
Yes ___ No___
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