Punnett squares
The tool which uses
the combination of
alleles to predict the
probability of traits
showing up in
offspring.
Green eyes are
dominant and yellow
eyes are recessive.
The genotype of two
insects are Gg and Gg.
Complete a Punnett square!
G
g
G
GG
Gg
g
Gg
??
?? = gg
What % of the young
would have green
eyes?
75%
Yellow eyes?
25%
If B=black and b=brown and
two wolves are heterozygous
Bb and homozygous bb what
would their young be?
Complete a Punnett square!
B
b
b
Bb
bb
b
Bb
bb
What % of young would
be black and what %
would be brown?
Black = 50 %
Brown = 50 %
B=Brown eyes which are
dominant, b=blue eyes
which are recessive
What are the alleles of
the parents for the
following chart?
B
b
B
BB
Bb
b
Bb
bb
The parents would be
Bb and Bb and both
would have brown
eyes!
Curly hair is dominant,
and a couple have curly
hair. How many of
their babies will have
curly hair?
A. All of the babies
B. Probably most of
the babies
C. None of the
babies
Answer - B
What percent of your
genes come from each
parent?
50%
What % of genes
come from each
grandparent?
25%
If green snake skin
is dominant and
yellow is recessive,
what are the alleles
of the parent snakes
for the following:
G
G
g
Gg
Gg
g
Gg
Gg
Homozygous (GG)
green
Homozygous (gg) yellow
How many different
Punnett squares can you
think of?
If big ears are
dominant and both
parents are
homozygous dominant,
what percent of babies
will have big ears?
E
E
E
EE
EE
E
EE
EE
100%
Three fingers is dominant
and five fingers
recessive. If mom is
homozygous dominant and
dad is heterozygous,
what percent of young
will have three fingers?
F
F
F
FF
FF
f
Ff
Ff
100%
Big noses are dominant
and little noses are
recessive. If Dad is
homozygous dominant and
mom is homozygous
recessive, what percent
of children will have big
honkers?
N
N
n
Nn
Nn
n
Nn
Nn
100%
Short is dominant and
tall is recessive. If dad
is heterozygous dominant
and mom is homozygous
recessive, what percent
of the children will be
short and tall?
S
s’
s’
Ss’
s’s’
s’
Ss’
s’s’
50% short
50% tall
Long neck is dominant and
short neck is recessive.
If dad is heterozygous
dominant and mom is
heterozygous dominant,
what percent of the
children will have long
necks and short necks?
N
n
N
NN
Nn
n
Nn
nn
75% Long
25% Short
Short tongues are
dominant and long are
recessive. If mom is
homozygous recessive
and dad is homozygous
recessive, what percent
of the children will have
long tongues?
t
t
t
tt
tt
t
tt
tt
100%
CROSSING TWO TRAITS
• CROSS A HOMOZYGOUS TALL ,
HETEROZYGOUS GREEN PEA PLANT
WITH A HOMOZYGOUS SHORT,
HOMOZYGOUS YELLOW PLANT.
• TTGg X ttgg
4
3
TTGg
7
x
8
ttgg
1
5
6
2
1
TG
2
3
4
Tg
TG
Tg
TtGg
Ttgg
5
tg
6
tg
7
TtGg
TtGg
TtGg
Ttgg
Ttgg
TtGg
Ttgg
Ttgg
TtGg
Ttgg
tg
8
tg
TtGg
Ttgg
TtGg
Ttgg
1
TG
5
tg
6
tg
7
tg
8
tg
X
2
3
4
Tg
TG
Tg
X
Ttgg
X
TtGg
Ttgg
TtGg
X
Ttgg
TtGg
X
Ttgg
X
TtGg
X
Ttgg
X
TtGg
TtGg
Genotypes and percentages
Phenotypes and percentages
X
TtGg
X
TtGg
X
X
TtGg = 8/16
Heterozygous Tall
Heterozygous Green
X
X
Ttgg
X
Ttgg
X
Ttgg
Ttgg = 8/16
Heterozygous Tall
Homozygous Yellow
Thank you