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Probability and The
Punnett Square
Gaiser Life Science
Know
Probability and The Punnett Square
What are the chances of flipping a coin and landing on tails?
Explain your answer.
Evidence
The Punnett Square
Page 37
Clarifying ?s
Probability and The Punnett Square
Information
probability
- The chance/likelihood that something will happen
Punnett
Square
- a chart that shows all possible genetic crosses
Example: flipping a coin – 50/50 chance of
landing on heads (50/50, 1 in 2, 1:1, ½, 50%)
- Mendel was the first scientist to determine that
probability could be used to predict genetic crosses.
used to determine the probability of a specific outcome
- Reginald C. Punnett originated the Punnett Square.
Example: Dad’s alleles = Tt, Mom’s alleles = TT
T t
T TT Tt
T TT tT
25% 25%
25% 25%
1 in 4 chance of a specific outcome
Offspring has a 100% chance of being tall.
Page 38
Clarifying ?s
Probability and The Punnett Square
Information
genotype
- an organism’s genetic make-up
phenotype
- an organism’s physical appearance/visible
traits pheno = physical
homozygous
heterozygous
codominance
Example: Tt
Example: being tall
- two identical alleles
Example: TT or tt
- two different alleles
Example: Tt
- alleles are neither dominant or recessive – both
show up in offspring
Example: black chickens & white chickens – the
offspring have both black and white feathers
Summary:
Page 39
Clarifying ?s
Probability and The Punnett Square
Information
probability
- The chance/likelihood that something will happen
Punnett
Square
- a chart that shows all possible genetic crosses
Example: flipping a coin – 50/50 chance of
landing on heads (50/50, 1 in 2, 1:1, ½, 50%)
- Mendel was the first scientist to determine that
probability could be used to predict genetic crosses.
- Reginald C. Punnett originated the Punnett Square.
used to determine the probability of a specific outcome
Example: Dad’s alleles = Tt, Mom’s alleles = TT
T t
T TT Tt
T TT tT
25% 25%
25% 25%
1 in 4 chance of a specific outcome
Offspring has a 100% chance of being tall.
Page 38
Clarifying ?s
Probability and The Punnett Square
Information
genotype
- an organism’s genetic make-up
phenotype
- an organism’s physical appearance/visible
traits pheno = physical
homozygous
heterozygous
codominance
Example: Tt
Example: being tall
- two identical alleles
Example: TT or tt
- two different alleles
Example: Tt
- alleles are neither dominant or recessive – both
show up in offspring
Example: black chickens & white chickens – the
offspring have both black and white feathers
Summary:
Page 39
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