Genotype and Phenotype

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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 codes for a protein or RNA, thereby controlling an inherited characteristic.

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Example: This image shows that a gene is a specific section of a DNA molecule, which is tightly packed into 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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A variant form of a specific gene, with each individual inheriting one allele from each parent for a trait.

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Example: This diagram shows that an allele is a version of a gene located at a specific position (locus) on each chromosome in a homologous pair.

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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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The allele that is fully expressed in the phenotype of an organism when at least one copy is present.

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Example: The diagram shows that the dominant 'B' allele produces a functional protein, resulting in brown eyes even when paired with a non-functional 'b' allele.

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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 whose characteristic is only expressed in the phenotype when two copies are present in the genotype.

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Example: This diagram shows that a recessive allele (labeled 'a') is a gene variant that is masked by a dominant allele ('A') in a heterozygous pair (Aa).

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Genotype Noun

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[jee-noh-tiep]

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Genotype

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The specific genetic makeup of an organism, representing the combination of alleles it has inherited from its parents.

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Example: This diagram shows genotype as the combination of alleles (letters like 'A' or 'a') on a pair of chromosomes, illustrating homozygous and heterozygous examples.

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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 or traits of an organism, resulting from the expression of its specific genotype.

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Example: This diagram shows how an organism's genotype (the combination of alleles, like AA, Aa, or aa) determines its phenotype (the observable physical trait, like brown or blue eyes).

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Homozygote Noun

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[hoh-moh-zy-goht]

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Homozygote

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An organism that has inherited two identical alleles for a particular gene from its parents.

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Example: This image shows a homozygous genotype, where an individual has two identical alleles for a gene (like BB or bb) on a pair of chromosomes.

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Homozygous dominant Noun

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[hoh-moh-zy-guhs dom-uh-nuhnt]

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Homozygous dominant

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A genotype characterized by the presence of two identical dominant alleles for a specific genetic trait.

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Example: This image shows a pair of chromosomes with two identical dominant alleles (BB), which is the definition of a homozygous dominant genotype.

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Homozygous recessive Noun

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[hoh-moh-zy-guhs ri-ses-iv]

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Homozygous recessive

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A genotype characterized by the presence of two identical recessive alleles for a specific genetic trait.

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Example: This diagram shows a pair of chromosomes with two identical lowercase alleles (aa), representing a homozygous recessive genotype for a specific trait.

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Heterozygote Noun

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[het-er-oh-zy-goht]

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Heterozygote

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An organism that has inherited two different alleles for a particular gene from its parents.

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Example: The image shows a pair of chromosomes with different versions (alleles) of a gene, one labeled 'B' and the other 'b', making it heterozygous.