Punnett Squares

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Gene Noun

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[jeen]

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Gene

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A segment of DNA that codes for a single protein or RNA, controlling the expression of inherited characteristics.

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

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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, such as eye color or height, which is determined by its genes.

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Example: This image shows that a trait is determined by genes on chromosomes. The different versions of a gene, called alleles (B and b), combine to form the genetic code for a specific characteristic.

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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: This image shows that alleles are different versions of a gene (like 'A' and 'a') located on paired chromosomes, determining if an organism is homozygous or heterozygous.

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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 fully expressed in the phenotype of a heterozygote, masking the effect of the recessive allele.

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Example: This Punnett square shows that when the dominant allele for purple flowers (B) is present, it determines the flower's color, even with a recessive allele (b).

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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 phenotypic effect is observed only when two copies are present in the genotype of an organism.

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Example: This diagram shows a recessive allele ('a') in two situations: paired with a dominant allele ('Aa') and paired with another recessive allele ('aa').

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Genotype Noun

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[jee-noh-tahyp]

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Genotype

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The specific genetic makeup of an organism, representing the combination of alleles inherited for a particular gene or set of genes.

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Example: The image shows how different combinations of alleles (A, a) on chromosomes create different genotypes, such as homozygous (AA, aa) and heterozygous (Aa).

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Phenotype Noun

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[fee-noh-tahyp]

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Phenotype

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The set of observable physical characteristics of an individual resulting from the interaction of its genotype with the environment.

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Example: This image shows how an organism's genetic makeup (genotype) determines its observable physical traits (phenotype), using eye color as an example.

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Homozygote Noun

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[hoh-moh-zahy-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, such as BB or bb.

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Example: This diagram shows that a homozygote has two identical alleles (e.g., BB or bb) for a trait, located on a pair of homologous chromosomes.

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Heterozygote Noun

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[het-er-oh-zahy-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, such as the genotype Bb.

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Example: This image shows a pair of homologous chromosomes with different versions (alleles) of a gene, labeled 'B' and 'b', representing a heterozygous individual.

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Punnett Square Noun

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[puhn-it skwair]

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Punnett Square

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A diagram used to predict the probability of an offspring having a particular genotype based on the parents' genotypes.

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Example: This Punnett square shows how alleles from a brown-eyed parent (BB) and a blue-eyed parent (bb) combine, resulting in all brown-eyed offspring (Bb).