Patterns of Reproduction

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Trait Noun

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[trayt]

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Trait

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Any observable feature or characteristic of an organism, resulting from the expression of its genes and environmental factors.

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Example: This family tree chart shows how a specific trait, represented by the red squares, is passed down from parents to their children across generations.

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Inherited Trait Noun

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[in-her-it-ed trayt]

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Inherited Trait

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A specific characteristic that is genetically determined and passed from parents to their offspring through genes.

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Example: This diagram shows a simple family tree, with a parent generation at the top and an offspring generation at the bottom, illustrating the structure of inheritance.

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Acquired Trait Noun

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[uh-kwy-erd trayt]

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Acquired Trait

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A characteristic that an organism develops during its lifetime due to environmental influences, learning, or injury.

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Example: A scar is an acquired trait because it develops on the skin after an injury and is not something a person is born with.

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Gene Noun

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[jeen]

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Gene

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A specific segment of DNA that contains the instructions for building a protein, which in turn influences a trait.

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Example: This diagram shows that a gene is a specific section of a DNA molecule, which is found on a chromosome inside a cell's nucleus.

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Allele Noun

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[uh-leel]

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Allele

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One of two or more alternative forms of a gene that are found at the same place on a chromosome.

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Example: An allele is a specific version of a gene. The letters 'A' and 'a' on the chromosomes represent two different alleles for the same gene.

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Genotype Noun

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[jee-noh-type]

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Genotype

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The specific combination of alleles an organism possesses for a particular gene, often represented by letters.

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Example: A genotype is the specific combination of alleles (versions of a gene) on an organism's chromosomes, shown here as AA, Aa, or aa.

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Phenotype Noun

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[fee-noh-type]

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Phenotype

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The set of observable physical or biochemical characteristics of an organism, determined by its genotype and environment.

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Example: This image shows that an organism's genetic code (genotype) determines its observable physical traits (phenotype), like the normal or wrinkled wings of a fruit fly.

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Homozygous Adjective

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[hoh-moh-zy-gus]

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Homozygous

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Describes a genotype having two identical alleles for a particular gene at the corresponding loci on homologous chromosomes.

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Example: This image shows that homozygous means having two identical alleles (like AA or aa) for a gene on a pair of chromosomes.

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Heterozygous Adjective

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[het-er-oh-zy-gus]

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Heterozygous

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Describes a genotype having two different alleles for a particular gene at the corresponding loci on homologous chromosomes.

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Example: This image shows a pair of chromosomes with two different alleles for a gene (one 'B' and one 'b'), which defines the heterozygous state.

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Dominant Allele Noun

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[dom-i-nant uh-leel]

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Dominant Allele

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An allele that expresses its phenotypic effect even when only one copy is present in a heterozygous genotype.

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Example: This diagram shows that a dominant allele (B) determines the trait (brown eyes) even when a recessive allele (b) is also present.