Transcript Document

A model used to show the
possible ways genes can
combine during fertilization.
Punnett Squares
Helps you keep
track of traits.
Punnett Squares
.
Dominant and recessive alleles
are represented by letters.
Punnett Squares
A capital letter (T) is used for
dominant alleles.
Punnett Squares
A lowercase letter (t) is
used for recessive alleles.
Punnett Squares
If you wanted to know the type of offspring
a cross between two parents would
produce, you can use a punnett square.
Tt x Tt
TT,Tt for tall
Tt for short
Punnett Squares
The letters representing the alleles from
one parent are placed along the top of the
square.
T
t
Punnett Squares
The letters representing the two alleles from the second
Parent are places along the side of the square.
T
t
Punnett Squares
T t xT t
T
T
t
t
Punnett Squares
Squares are filled by writing the letter at the
top beside the letter on the side.
T
T
TT
t
Tt
t
Tt
tt
Punnett Squares
The letters in each of the squares
represents the Genotypes of the offspring
that the parents could produce.
T
T
TT
t
Tt
t
Tt
tt
TT
Tt
Tt
tt
Punnett Squares
The genotype (genetic makeup)
can be used to predict the
phenotype (physical appearance)
of the offspring.
Punnett Sqaures
Genotype
TT
Tt
Tt
tt
Phenotype
tall
tall
tall
short
Punnett Squares
Probability: the ratio that a particular event
could occur.
out of 4 offspring
3 would be tall
1 would be short
Punnett Squares:
•Help you keep track of traits.
•Predict genotype and phenotype.
•Calculate probability.