Heredity and Punnett Squares

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What is heredity?

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The passing of traits from parents to offspring through genes.

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What is a Punnett square?

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A diagram used to predict the outcome of a genetic cross by showing the possible allele combinations from the parents.

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What does homozygous mean?

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Having two identical alleles for a particular gene (e.g., AA or aa).

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What does heterozygous mean?

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Having two different alleles for a particular gene (e.g., Aa).

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What is a dominant allele?

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An allele that expresses its trait even when only one copy is present (e.g., T in Tt).

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What is a recessive allele?

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An allele that only expresses its trait when two copies are present (e.g., aa).

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What is a phenotype?

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The visible or physical trait resulting from the allele pair (e.g., brown hair).

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What is a genotype?

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The genetic combination of alleles in the allele pair (e.g., AA, Aa, or aa).

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How do you calculate the probability of an offspring's trait using a Punnett square?

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Count the number of times the desired trait appears in the offspring combinations and divide by the total number of combinations.

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What does it mean if a trait is expressed in 25% of the offspring?

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There is a 25% chance that any given offspring will express that trait.