Genetics: Punnett Square

Front

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 does homozygous mean?

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Homozygous refers to having two identical alleles for a particular gene, such as AA or aa.

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What does heterozygous mean?

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Heterozygous refers to having two different alleles for a particular gene, such as Aa.

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What is a phenotype?

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Phenotype is the observable physical or biochemical characteristics of an organism, determined by its genotype.

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What is a genotype?

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Genotype is the genetic makeup of an organism, representing the alleles it carries for a specific gene.

Front

If a white flower (rr) is crossed with another white flower (rr), what is the phenotype of the offspring?

Back

100% white.

Front

If a white flower (rr) is crossed with another white flower (rr), what is the genotype of the offspring?

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100% homozygous recessive (rr).

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If a tall plant (Tt) is crossed with a short plant (tt), what is the phenotype of the offspring?

Back

50% tall; 50% short.

Front

If a tall plant (Tt) is crossed with a short plant (tt), what is the genotype of the offspring?

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50% heterozygous (Tt); 50% homozygous recessive (tt).

Front

What is the expected phenotype ratio from a cross between a homozygous dominant (BB) and a heterozygous (Bb) organism?

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100% brown.