Punnett Squares

Front

What is a Punnett Square?

Back

A Punnett Square is a diagram used to predict the genetic makeup of offspring from a particular cross or breeding experiment.

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What does phenotype mean?

Back

Phenotype refers to the physical appearance or observable traits of an organism.

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What does genotype mean?

Back

Genotype refers to the genetic makeup of an organism, specifically the alleles it possesses.

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What is the difference between homozygous and heterozygous?

Back

Homozygous means having two identical alleles for a trait (e.g., AA or aa), while heterozygous means having two different alleles for a trait (e.g., Aa).

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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 in the genotype.

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What is a recessive allele?

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A recessive allele is an allele that only expresses its trait when two copies are present in the genotype.

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How do you calculate the percentage of offspring with a specific phenotype?

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You can calculate the percentage by using a Punnett Square to determine the ratio of phenotypes and then converting that ratio into a percentage.

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If both parents are heterozygous (Aa), what is the expected phenotype ratio of their offspring?

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The expected phenotype ratio is 3:1, meaning 75% will show the dominant trait and 25% will show the recessive trait.

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What is the expected genotype ratio from a cross between two heterozygous parents (Aa x Aa)?

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The expected genotype ratio is 1 AA : 2 Aa : 1 aa.

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What does it mean if an organism is homozygous recessive?

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It means the organism has two identical recessive alleles for a trait (e.g., aa).