Download Dominant/Recessive

Name _____________________________________________ Date ____________ Period ______
BACKGROUND: A long time ago, in a galaxy far, far away, a great race of beings lived on a planet
called ZORK. The inhabitants were known as Zorkonians. Remember our friends from ZORK.
They are made up of 10 basic genes that code for their traits. Each one of these genes is made up
2 alleles.
 With this in mind, there are 1,024 different possible combinations for their appearance!
 If we look at their genes, there are 59,049 different combinations of the alleles!
Vocabulary Reminders!!
Gene
Allele
Hair color
1. Green color = G
2. Yellow color = g
Example: There is a gene for hair color in a zork. The alleles possible for hair color would be green (G) and yellow (g).
There are 2 alleles for each gene and we use letters for each allele. The capital letters are the dominant alleles and the
lower case letters are the recessive alleles. One letter or allele is inherited from each parent.
Dominant: Only one copy of the dominant allele is required for the dominant trait to show. Example: GG or Gg
Recessive: two recessive alleles are required for the trait to show up. Example: gg
Phenotype: The physical appearance or what the gene makes an organism look like. Examples would be two eyes, yellow
hair, and green lips from a zork.
Genotype: The genetic makeup of an organism. We use letters for the genotype. Remember that you need to look at the
genotype to see what the phenotype will be.
Heterozygous/Hybrid: The term used for different alleles. There is always one dominant and one recessive allele.
Example: Gg.
Homozygous/Purebred: The term used for having the same alleles. 2 dominant alleles or 2 recessive alleles.
Example: GG- homozygous dominant OR gg- homozygous recessive.
Practice Problems
1. For each genotype, indicate whether it is heterozygous (HE), homozygous recessive (HR), or homozygous
dominant (HD).
Hh_______
tt_______
Ee_______
rr_______
Ff_______
TT_______
LL_______
FF_______
bb_______
Ww_______
GG_______
Nn_______
2. For each genotype below, determine the phenotype.
Two horns are dominant to one horn.
HH__________________________
Hh___________________________
hh___________________________
One eye is dominant to three eyes.
EE__________________________
Ee___________________________
ee___________________________
Two wings are dominant to no wings.
WW__________________________
Ww___________________________
ww___________________________
Yellow skin is recessive to green skin.
YY___________________________
Yy___________________________
yy___________________________
3. For each phenotype below, determine the genotype(s) possible.
Green hair is dominant to yellow hair.
Two legs are recessive to one leg.
Green _______________ Yellow _______________
One leg _______________ Two legs _______________
Purple lips are dominant to green lips.
One fang is dominant to two fangs.
Purple _______________ Green _______________
One fang ______________ Two fangs ______________
Please refer back to this to help you as you work through this assignment. You will use the table below to complete the
problems that follow. Everything you need is in the table! The following are the traits of a Zork, which we will use to study
genetics. You will be studying one family. Be sure to read each problem carefully, because in each case the information is
built upon the previous problem.
Allele
T
t
G
g
E
e
F
f
H
h
L
l
W
w
N
n
R
r
B
b
Dominant/Recessive Genotype Phenotype Heterozygous Homozygous
Trait
Tall
Dominant
TT,Tt
Tall
Tt
TT
Short
Recessive
tt
Short
tt
Green
Green
Dominant
GG,Gg
Gg
GG
hair
Hair
Yellow
Yellow
Recessive
gg
gg
hair
Hair
One Eye
Dominant
EE,Ee
One Eye
Ee
EE
Three
Three
Recessive
ee
ee
Eyes
Eyes
One
Dominant
FF,Ft
One Fang
Ff
FF
Fang
Two
Two
Recessive
ff
ff
Fangs
Fangs
Two
Two
Dominant
HH,Hh
Hh
HH
Horns
Horns
One
Recessive
hh
One Horn
hh
Horn
Purple
Purple
Dominant
LL,Ll
Ll
LL
Lips
Lips
Green
Green
Recessive
ll
ll
Lips
Lips
Two
Two
Dominant
WW,Ww
Ww
WW
Wings
Wings
No
Recessive
ww
No Wings
ww
Wings
One Leg
Dominant
NN,Nn
One Leg
Nn
NN
Two
Recessive
nn
Two Legs
nn
Legs
Green
Green
Dominant
RR,Rr
Rr
RR
Skin
Skin
Yellow
Yellow
Recessive
rr
rr
Skin
Skin
Thick
Thick
Dominant
BB,Bb
Bb
BB
Eyebrow
Eyebrow
Thin
Thin
Recessive
bb
bb
Eyebrow
Eyebrow
Name _____________________________________________ Date ____________ Period ______
4. Cross a heterozygous green skinned zork with a yellow skinned zork.
A. Parents ______ x _______
B. Genotypes: ____GG: ____Gg: ____gg
C. Phenotypes: _______Green ______Yellow
D. What percentage of yellow skinned zorks are possible? _________%
5.
A.
B.
C.
D.
Cross a homozygous two horned zork with a heterozygous two horned zork.
Parents ______ x _______
Genotypes:
Phenotypes:
What percentage of two horned zorks are possible? _________%
6.
A.
B.
C.
D.
Cross a heterozygous green haired zork with a heterozygous green haired zork.
Parents ______ x _______
Genotypes:
Phenotypes:
What percentage of green haired zorks are possible? _________%
7.
A.
B.
C.
D.
Cross a green lipped zork with a heterozygous purple lipped zork.
Parents ______ x _______
Genotypes:
Phenotypes:
What percentage of purple lipped zorks are possible? _________%
8. Tork, who is homozygous for his tall height meets Vorkina, who is short. Vorkina’s family brags that they are a
“purebred” line. Tork says he is purebred too. Tork asked Vorkina to marry him and she said YES. Create a
Punnett square to show the possibilities that would result if Tork and Vorkina has children. Use T to represent the
dominant gene.
A. Genotypes:
B. Pheonotypes:
C. What are the chances that a child will be tall?
D. What are the chances that a child will be short?
E. Would Tork and Vorkina’s children still be considered purebred? Explain.
9. Tork and Vorkina have two children. One is a boy named Torky and the other is a girl named Vorki. Thinking about
what you know about Torky from question #8. What would happen if Torky meets and marries a girl named
Morkalina who is short. Create a Punnett square to show the possibilities that would result if they had children.
A. Parents _______ x ________
B. Genotypes:
C. Pheonotypes:
D. What are the chances that a child will be tall?
E. What are the chances that a child will be short?
10. Vorki, the daughter(from #8), meets a zork named Spork, both are heterozygous for two wings. They recently had
a new baby zork. Vorki has been upset since she first saw her baby who has no wings. She claims the hospital
made a mistake and mixed up her baby with someone else’s baby. Create a Punnett square to determine if the
hospital made a mistake. Explain your answer.
11. Torky has green hair and Morkalina has yellow hair. They really want children with their mother’s yellow hair. What
phenotype and genotype must Torky be to create children with yellow hair? Explain.
12. Vorki is famous for her three eyes, which are the prettiest eyes in all of zork. She falls in love and marries Spork,
who also has three eyes. Would it be possible for them to have children who didn’t have three eyes? Explain.