Other Patterns of Inheritance

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Incomplete Dominance Noun

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[in-kuhm-pleet dom-uh-nuhns]

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Incomplete Dominance

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A pattern of inheritance where one allele is not completely dominant, resulting in a heterozygous phenotype that is a blend.

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Example: Crossing a red flower with a white flower produces pink offspring because neither the red nor the white allele is completely dominant.

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Codominance Noun

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[koh-dom-uh-nuhns]

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Codominance

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A genetic scenario where the phenotypes produced by both alleles are clearly and separately expressed in a heterozygous individual.

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Example: When a white chicken (WW) and a black chicken (BB) have offspring, the result is a speckled chicken (BW) that shows both black and white feathers.

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Multiple Alleles Noun

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[muhl-tuh-puhl uh-leelz]

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Multiple Alleles

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The existence of a gene in more than two different forms, or alleles, within a given population.

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Example: This diagram shows that a single gene for rabbit fur color has more than two versions (alleles), leading to four different fur patterns (phenotypes).

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Polygenic Trait Noun

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[pol-ee-jen-ik treyt]

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Polygenic Trait

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A characteristic that is controlled by the interaction of two or more genes, often showing a wide phenotypic range.

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Example: This diagram shows that polygenic traits, like human height, create a continuous range of variations, with most individuals clustering around an average value.

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Allele Noun

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[uh-leel]

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Allele

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One of the different forms or variations of a specific gene that can exist at a genetic locus.

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Example: Alleles are versions of a gene found at the same location (locus) on each chromosome in a homologous pair.

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Gene Noun

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[jeen]

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Gene

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A specific sequence of DNA that codes for a functional product, such as a protein, and determines a trait.

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Example: This diagram shows that a gene is a specific segment of a DNA molecule, which is tightly coiled to form a chromosome inside a cell's nucleus.

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Phenotype Noun

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[fee-noh-tiep]

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Phenotype

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The observable physical characteristics of an organism, as determined by both genotype and environmental influences.

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Example: This diagram shows how different allele combinations (genotypes like AA, Aa, aa) on chromosomes determine an organism's observable physical trait (phenotype), such as eye color.

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Genotype Noun

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[jee-noh-tiep]

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Genotype

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The specific combination of alleles that constitutes the genetic makeup of an organism for a particular trait.

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Example: This image shows the three types of genotypes: homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa), representing an organism's specific allele combination.

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Heterozygous Adjective

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[het-er-oh-zy-guhs]

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Heterozygous

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Describing an organism that has two different alleles for a particular gene at corresponding loci on homologous chromosomes.

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Example: This image shows a pair of homologous chromosomes with two different alleles (A and a) for the same gene, which defines the heterozygous condition.

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Homozygous Adjective

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[hoh-moh-zy-guhs]

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Homozygous

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Describing an organism that has two identical alleles for a particular gene at corresponding loci on homologous chromosomes.

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Example: This diagram shows that a homozygous genotype has two identical alleles for a trait, like 'AA' or 'aa', on a pair of chromosomes.