2.6 Predicting Traits

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The genetic makeup of an organism, represented by the combination of alleles (e.g., BB, Bb, or bb) that determine specific traits.

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Genotype

Front

The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences (e.g., hair color, height).

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Phenotype

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Different versions of a gene that determine specific traits. For example, in the case of eye color, the allele for brown eyes and the allele for blue eyes are different alleles of the same gene.

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Allele

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A trait that is expressed in the phenotype when at least one dominant allele is present in the genotype (e.g., tall pea plants represented by the allele T).

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Dominant Trait

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A trait that is only expressed in the phenotype when two recessive alleles are present in the genotype (e.g., short pea plants represented by the allele t).

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Recessive Trait

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A genetic relationship in which both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows both traits (e.g., AB blood type).

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Codominance

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A genetic situation in which one allele is not completely dominant over another, resulting in a phenotype that is a blend of both alleles (e.g., red and white flowers producing pink flowers in snapdragons).

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Incomplete Dominance

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A genetic cross that examines the inheritance of a single trait, involving two parents that differ in one specific allele (e.g., crossing a homozygous dominant tall plant (TT) with a homozygous recessive short plant (tt) to analyze the offspring's traits).

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Monohybrid Cross

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A diagram used to predict the genetic outcomes of a cross between two organisms, showing the possible allele combinations of offspring based on the parental genotypes.

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Punnett Square