S.7.2.3 Review - Punnett Squares

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What is a Punnett Square?

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A Punnett Square is a diagram used to predict the outcome of a genetic cross by showing the possible combinations of alleles from the parents.

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What do the letters in a Punnett Square represent?

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The letters represent the alleles of the genes being crossed, with uppercase letters indicating dominant alleles and lowercase letters indicating recessive alleles.

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What is the genotype of an organism?

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The genotype is the genetic makeup of an organism, represented by the combination of alleles (e.g., PP, Pp, pp).

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What is the phenotype of an organism?

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The phenotype is the physical appearance or observable traits of an organism resulting from its genotype.

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What does homozygous mean?

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Homozygous refers to having two identical alleles for a particular gene (e.g., PP or pp).

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What does heterozygous mean?

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Heterozygous refers to having two different alleles for a particular gene (e.g., Pp).

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If a pea plant has the genotype Pp, what are the possible phenotypes?

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The possible phenotypes are purple flowers (dominant trait) since P is dominant over p.

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What is the expected phenotype ratio from a cross between two heterozygous pea plants (Pp x Pp)?

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The expected phenotype ratio is 3:1, with 3 purple-flowered plants for every 1 white-flowered plant.

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What is the expected genotype ratio from a cross between two heterozygous pea plants (Pp x Pp)?

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The expected genotype ratio is 1:2:1, with 1 PP, 2 Pp, and 1 pp.

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What is a dominant allele?

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A dominant allele is an allele that expresses its trait even when only one copy is present (e.g., P in Pp).