Variation of Traits

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Heredity Noun

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[huh-red-i-tee]

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Heredity

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The passing of traits or characteristics from parents to offspring through their genes.

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Example: This family tree, called a pedigree chart, shows how a trait (red color) is passed from parents to their children through different generations.

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Genetics Noun

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[juh-net-iks]

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Genetics

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The scientific study of heredity and the variation of inherited characteristics in organisms.

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Example: This diagram shows how our genetic instructions are organized, starting from a cell, zooming into the nucleus, then a chromosome, and finally to a gene on a DNA strand.

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Trait Noun

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[trayt]

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Trait

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A specific, observable characteristic of an organism, determined by genes and the environment.

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Example: This image shows that finches have different beak shapes, which is a physical trait that helps them eat different types of food.

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Gene Noun

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[jeen]

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Gene

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A unit of information passed from parent to offspring that determines a specific trait.

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Example: This image shows that a gene is a specific section of a DNA molecule, which is coiled to form a chromosome inside a cell.

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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 of a specific gene, which determines the expression of a particular trait.

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Example: This image shows alleles as different versions of a gene on a chromosome, represented by the letters B and b.

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Dominant Allele Noun

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[dom-uh-nuhnt uh-leel]

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Dominant Allele

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An allele that is expressed in an organism's appearance, masking the effect of a recessive allele when present.

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Example: This diagram shows that a plant with one 'Tall' allele (T) and one 'dwarf' allele (t) is still tall, proving the 'T' allele is dominant.

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Recessive Allele Noun

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[ri-ses-iv uh-leel]

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Recessive Allele

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An allele that is masked by a dominant allele and is only expressed if two copies are present.

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Example: This diagram shows a recessive allele ('a') on a chromosome, which is only expressed as a trait when two copies are present ('aa').

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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 genetic trait.

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

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Phenotype Noun

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[fee-noh-type]

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Phenotype

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

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Example: This chart shows that a phenotype is the physical trait you can see, like eye color, which is determined by an individual's genes (genotype).

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Homozygous Adjective

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[hoh-moh-zy-guhs]

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Homozygous

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Describes a genetic condition where an individual has two identical alleles for a particular gene.

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Example: This diagram shows a pair of chromosomes with two identical alleles (like 'AA' or 'aa'), which is what homozygous means for a gene.