Transcript 11.2

Objective: to be able to create
punnett squares and predict
probabilities of the outcome
11.2
Probability
Probability: how likely it is for
something to happen
Ex: coin flip= 1 out of every 2 flips
should be heads=1/2 or 50%
If a coin is flipped 3 times how
likely is it to be heads every time?
1/2x1/2x1/2= 1/8
Punnett Square
Probability can be used to predict
outcome of genetic crosses
Punnett Squares= used to predict
The parents are on the top and
side of the punnett square and
the offspring are in the middle of
the punnett square.
One parent
T= tall
t= short
T
T
One
parent
t
t
TT
Tt
Tt
tt
Homozygous:
both alleles are the same TT or tt
Heterozygous:
both alleles are different Tt
Phenotype:
what the trait appears the be (tall or
short)
Genotype:
what the alleles are (TT, Tt, tt)
When you cross 2 heterozygous
organisms: you always get ¼ TT, ½
Tt, and ¼ tt.
Probabilities are more accurate the
more organisms you are comparing
Ex: coin flipping is going to be 1/2 , but
you are more likely to see this the
more coins you flip.