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Dihybridcrossesworksheet

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Name:
Period:
Dihybrid crosses practice problems
1. Dobby the House Elf falls head over heels for Elf-ette named Dabbin’. The marry and
decide to raise a family of little house elves. Dobby’s pointed ears are dominant, and
knows that he is heterozygous for ear shape. Dabbin’s ears are round. Dobby’s long
nose is a recessive trait, and Dabbin’ is homozygous dominant for her stubby nose.
Using a Punnett square, determine the probability that they will have an elf child with a
stubby nose and pointed ears. Fill in the Punnett square below to support your answer.
Dobby genotype:
Dabbin genotype:
2. Hagrid has been breeding his creatures again. This time he is breeding Cerberus, his 3 headed dog. Having three heads
is dominant over having 2 heads. He has also discovered that having chocolate brown fur is dominant to
yellow fur. Hagrid crosses Cerberus (who is heterozygous for both traits) to a female that is also
heterozygous for both traits. Hagrid’s customers want the super rare 2-headed, yellow furred dogs. What
is the expected frequency of these dogs in the cross he conducts? Use the Punnett square below to
support your answer.
Name:
Period:
3. Gru needs a minion army – his regular minions are too incompetent, and he wants to hybridize them
with the evil purple minions. He knows that purple color is a recessive trait, and that 2
eyes is dominant to one eye. Gru wants an army of two eyed, purple minions. Gru breeds
2 minions that are heterozygous for both traits and produces 144 minion babies. How
many of these minions should be purple and have 2 eyes? Use the Punnett square below
to support your answer, and be sure to show all of your work.
4. Gru knows that his purple army can be supported by a steady diet of bananas, and that this is the source of their
strength. Unfortunately, there is a rare, recessive mutation that causes minions to be allergic to
bananas (tolerance to bananas, B, is a dominant trait). Another rare mutation, t, cases minions to be
toothless. Without teeth, they can’t even gum the bananas. Gru wants to breed 2 heterozygous
minions, and he is wondering what proportion of the offspring will be toothless and/or
allergic to bananas.
Name:
Period:
5. Mr. and Mrs. Incredible are expecting another baby! This time, they have done some research into some of
their incredible, super power genes, and they think they have an idea of what traits their new, incredible baby
will posses. Mr. Incredible’s strength is is a dominant trait, and he knows that he is heterozygous (Rr)
for his ridiculous strength. In contrast, Mrs. Incredible is homozygous dominant (EE) for her elastic
body. Mrs. Incredible lacks ridiculous super strength, and Mr. Incredible does not have elastic
body. What are the possible phenotypes of their baby?
6. You have decided to breed your little ponies, and you want to produce rarity – an albino
unicorn (both recessive traits to the dominant traits, yellow coat and lack of horn). You breed
a pony that is a unicorn and is heterozygous for coat color with a pony that is heterozygous
for lacking a horn and is white. What is the expected frequency of rarities in this cross?
Name:
Period:
Dihybrid crosses practice problems
1. Dobby the House Elf falls head over heels for Elf-ette named Dabbin’. The marry and
decide to raise a family of little house elves. Dobby’s pointed ears are dominant, and
knows that he is heterozygous for ear shape. Dabbin’s ears are round. Dobby’s long
nose is a recessive trait, and Dabbin’ is homozygous dominant for her stubby nose.
Using a Punnett square, determine the probability that they will have an elf child with a
stubby nose and pointed ears. Fill in the Punnett square below to support your answer.
Dobby genotype:
Eenn
Dabbin genotype:
E = pointy
e= round
N = stubby nose
n = long nose
eN
eeNN
En
en
EeNn
eeNn
50% chance (E-N-)
2. Hagrid has been breeding his
creatures again. This time he is breeding Cerberus, his 3 headed dog. Having three heads is dominant over
having 2 heads. He has also discovered that having chocolate brown fur is dominant to yellow fur. Hagrid
crosses Cerberus (who is heterozygous for both traits) to a female that is also heterozygous for both
traits. Hagrid’s customers want the super rare 2-headed, yellow furred dogs. What is the expected
frequency of these dogs in the cross he conducts? Use the Punnett square below to support your
answer.
HB
Hb
hB
hb
HB
HHBB
HHBb
HhBB
HhBb
Hb
HHBb
HHbb
HhBb
Hhbb
hB
HhBB
HhBb
hhBB
hhBb
hb
HhBb
Hhbb
hhBb
hhbb
H = 3 heads
h = 2 heads
B = chocolate
b = yellow
1/16 = 2-headed, yellow
Name:
Period:
3. Gru needs a minion army – his regular minions are too incompetent, and he wants to hybridize them
with the evil purple minions. He knows that purple color is a recessive trait, and that 2
eyes is dominant to one eye. Gru wants an army of two eyed, purple minions. Gru breeds
2 minions that are heterozygous for both traits and produces 144 minion babies. How
many of these minions should be purple and have 2 eyes? Use the Punnett square below
to support your answer, and be sure to show all of your work.
HB
Hb
hB
hb
H = yellow
h = purple
HB
HHBB
HHBb
HhBB
HhBb
B = 2 eyes
b = 1 eye
Hb
HHBb
HHbb
HhBb
Hhbb
hB
HhBB
HhBb
hhBB
hhBb
hb
HhBb
Hhbb
hhBb
hhbb
3/16 x 144 = 27 minions
should be hhB-
4. Gru knows that his purple army can be supported by a steady diet of bananas, and that this is the source of their
strength. Unfortunately, there is a rare, recessive mutation that causes minions to be allergic to
bananas (tolerance to bananas, B, is a dominant trait). Another rare mutation, t, cases minions to be
toothless. Without teeth, they can’t even gum the bananas. Gru wants to breed 2 heterozygous
minions, and he is wondering what proportion of the offspring will be toothless and/or
allergic to bananas.
BT
Bt
bT
bt
BT
BBTT
BBTt
BbTT
BbTt
Bt
BBTt
BBtt
BbTt
Bbtt
bT
BbTT
BbTt
bbTT
bbTt
bt
BbTt
Bbtt
bbTt
bbtt
B = tolerance
b = allergic to bananas
T = normal teeth
t = toothless
7/16 should either lack
teeth, be allergic to
bananas, or both
Name:
Period:
5. Mr. and Mrs. Incredible are expecting another baby! This time, they have done some research into some of
their incredible, super power genes, and they think they have an idea of what traits their new, incredible baby
will posses. Mr. Incredible’s strength is is a dominant trait, and he knows that he is heterozygous (Rr)
for his ridiculous strength. In contrast, Mrs. Incredible is homozygous dominant (EE) for her elastic
body. Mrs. Incredible lacks ridiculous super strength, and Mr. Incredible does not have elastic
body. What are the possible phenotypes of their baby?
E = elastic
e = normal
rE
Re
re
RrEe
rrEe
R = Strength
r = no super strength
(Rree x rrEE)
50% elastic, super strength
50% elastic, no super
strength
6. You have decided to breed your little ponies, and you want to produce rarity – an albino
unicorn (both recessive traits to the dominant traits, yellow coat and lack of horn). You breed
a pony that is a unicorn and is heterozygous for coat color with a pony that is heterozygous
for lacking a horn and is white. What is the expected frequency of rarities in this cross?
A = yellow
a = albino
Ah
ah
aH
AaHh
aaHh
ah
Aahh
aahh
H = hornless
h = unicorn
(Aahh x aaHh)
25% should be rarities (aahh)
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