Page 198 - Science Course 3 (Book 1)

Mo5-L2a: What is Punnett Square?

A Punnett square shows the probability of all
P Generation possible genotypes and phenotypes of offspring.
(true breeding
parents) This Punnett square predicts that 75 percent of the
offspring will express the dominant phenotype of
Purple White green pods.
Flowers Flowers

F Generation All plants have
1 G g
purple flowers

G
Fertilization among
F plants ( F x F ) GG Gg
1
1
1
F Generation
2
g

Gg gg
3 1
of plants of plants Phenotype – 3 green, 1 yellow
4
4
have purple have have Genotypes – 1 GG , 2 Gg , 1 gg
flowers flowers

P plants GENETIC MAKEUP (alleles) Key Concept
What is Punnett Square?
PP pp
How does a Punnet square help scientist predict
genetic outcomes?
Gametes All P All p

All Pp

1
1
F plants P P
1
(hybrids) 2 2
Gametes p P

Eggs PP Sperm
F Plants p p
2
Phenotypic ratio Pp Pp
3 purple : 1 white pp

Genotypic ratio
1PP : 2Pp : 1pp

SUMMARY
What is Punnett Square?

Scientists use Punnett squares and pedigrees
to predict and analyze genetic outcomes.

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