Genetics Practice Worksheet
Monohybrid Practice Problems
1. In horses, trotter (T) is dominant over pacer (t). A trotter is mated to a pacer, and the offspring is a pacer. Give the
genotype of all the horses.
a. Trotter’s genotype: Tt
b. Pacer’s genotype: ee
t
c. Offspring’s genotype: te
e
e) T
T
Te
te
2. In a paternity suit, the man has blood type AB. He could not be the father if the child has what blood type?
00
-
AI
00
3. A child with type O blood is born to a mother with type A blood.
a. What is the genotype of the child?
.
00
b. What is/are the possible genotype(s) of the mother?
AO
B
B
B
c. What is/are the possible genotype(s) of the father?
AO
,
BO
B
'
'
BB
BB
'
'
BB
BB
4. You breed horses. A chestnut horse (brown) with a genotype of BB is mated with a cremello horse (white) with a
genotype B’B’ and all the little ponies are palomino (beige). (Hint: ‘ indicates incomplete dominance of the trait)
a. What would be the genotype of the F1 horses?
'
BB
'
'
b. After crossing two F1 horses, what are the expected genotypic and phenotypic ratios of the F2 horses? Show a
punnett squares.
¥??%É
genotype
phenotype
Bj¥
=
=
1 BB
:
21313
'
1 Chestnut
cbnom ,
:/
:
B'B
2
'
Palomino
cbe.ge
:
loemdlo
unites
bb_
5. A heterozygous brown-eyed male has a child with a homozygous blue-eyed woman. What is the probability of the child
having brown eyes? Blue eyes? What is the genotypic ratio for 4 children based on the Punnett square?
50%
bbYBp.bg/bbbT-gen.+yperation-brown eyes
blue
eyes
13¥
:
:
501
.
" I
AB
6. A heterozygous woman with type B blood has a child with a type AB man. Show the Punnett Square and predict the
probability of the child having type B blood.
possibility of
type B blood
a.IE#:-Nnn-
-
=
50%
7. A heterozygous woman with normal color vision has a child with a colorblind man. Color blindness is a sex-linked trait.
-
How many, if any, of the children will also be colorblind? How many of them are girls and how many are boys?
Xn X^Ñ
☒
children
50% Of
'
could be colorblind
is girl
bae
1
.
.
RK
8. Red is incompletely dominant over white for the color of snapdragon petals. Starting with pure-bred parents, one red and
=
one white show the phenotypic ratios for F1 and F2 generations.
fl
4¥ :¥l
"
R
n
for
.
phenotype
=
phenotype
ratio
100% pink
=
1
red
:
ratio
2
pink :| white
Dihybrid Practice Problems
I
9. A pea plant true breeding with tall stem and round peas is crossed with a true-breeding pea plant with short stem and
WW
wrinkled peas. What is the genotype and phenotype of the F1 if tall and wrinkled are dominant? What are the
genotypic
and phenotypic ratios in the F2? Show the Punnett Square for F2.
④ Ttwwxttww
④ TW
④
TWTTWW
Tw
TW
tw
TTWwt-WWT-LWWT-wwxT-cww-gw-TWWTTww-t
.
l
k
ttwwttww
100%
Ttww
TW
±WT±WWTeWw
Tenn
T-LWWT-rwwttwwt-wn.tw④
Tw
+
W
hw
④ TW
Tw
+
genotypic
New
TWTTWWTTWWFLWWFLWW
ywTTWwTTwwT+WwT
Ww
WW
±WIWWT±Ww
" "
9
I
ttwwttww
Ttww Iww
④
tw
:
4:
I :z :| :|
phenotypic ratio
⇐
⇐
1:22
=
ratio
:
tall
tall
& Winkle
3
:
3
round
:
1
short
short
winkle
round
LL
RR
11
10. A pure-bred male fruit fly with red eyes and short wings is mated with a pure-bred female fly with white eyes and long
-
wings. If Red eyes and Long wings are dominant, indicate what the genotype and phenotype of the F1 would be. Then
show the punnett square for the second generation and list the phenotypic ratio.
-
⑤ 121211
⑥
'
00
✗
RRH
"
Rr4
t
rl
RHI
roll
Rrll
rrll
TI
E
IE
9 :3 :3 :|
rrLLm4
Rnli
Rrh
rf
Kru
121211
KRU
the Rue
RI
r
p.LK/zLLRR4RrLLRrLtphenotypRvatib
R,
€
R1
RL
rrLL
E
11. A pure-bred male mouse with black fur and solid coat is mated with a pure-bred female mouse with white fur and spots.
The first generation all have solid, black coats. What are the dominant and recessive alleles? Show the punnett square
for the F2 and list the phenotypic ratio.
dominant black fur
__
[ recessive
④ BBSS
④
100%
✗
-_
bbss
Bbss
→
BS
*
bs
bs
Solid coat
.
white fun
.
spotted coat
BS
Bs
bs
bs
Bless Bbss
BBSSBBSS
BS
Bbss
Boss
Bbs
,
Bs 13135s
bbss
bs Bbss
bs
Bss
Bbssbbss
Bbss
bbss
bbss
9 :S
:3 :L
bb
I
1-
¥
±
12. A pure-bred male shmoo that is round and has big ears is mated with a pure-bred female shmoo that is oval and has
small ears. If round and big ears are the dominant traits, what letters would you use to represent the parents and the F1
genotypes? What types of gametes can the F1 make based on their genotype? What is the phenotypic ratio in the
second generation?
④ RRBD
✗
⑤ RrBb_
RB
Rb
Brb
r
rrbb
RB
Rb
RB
rb
RB
Rb
RRBB
RRBB
r
Brb
RRBB RrBb
RrBr
RRBB Rkbb
RRBB RrBb
RrBb
Rrbb
krbb
MBB
rrBb
rrBb
trbb
9 :3 :3 :|
13. Ms. Johnston, Ms. Johnson, and Ms. Johnstone all entered the same hospital and gave birth to baby girls on the same
day, and all three babies were taken to the nursery to receive care, there. Someone later claimed that the hospital mixed
up the babies. As a hospital administrator, it is your job to make sure that each pair of parents has the correct baby, so
you order blood typing to be done on all the parents and all the babies. Here are the results:
Person
Blood Type Probable Genotype
(Phenotype)
Ms Johnston
A
AA or AO
Possible gametes
(eggs/sperm)
A
0
Bo
B
O
BBor BO
B
Mr Johnston
B
Ms Johnson
B
Mr Johnson
O
Ms Johnstone
A
Mr Johnstone
A
AA or A- 0
Baby A
O
00
Baby B
AB
Baby C
B
BB or
-
O O
AA
or
O
AO
A
A
O
O
0
0
AB
BB
or
130
1) For each parent, what possible genotype(s) could give that phenotype? If there’s more than one possible genotype,
then which of the possible genotypes would give the most variation in terms of possible children? Put that
genotype in the appropriate box, above, for each person.
2) For each parent, if that is his/her genotype, then what possible kinds of gametes can each produce? Put those in the
appropriate boxes, above.
3) So, now, who are the parents of which baby? (Hint: draw a Punnett square using the gametes from the chart to help)
1
Johnson
Johnston
Johnstone
:¥#÷IH¥%⇐H¥¥=o
a
o
t
"
Baby
B
Babyc
Baby A