Meiosis and Genetic Variation

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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 genetic traits or physical characteristics from parents to their offspring through genes.

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Example: This pedigree chart shows how a genetic trait is passed from parents to their children and grandchildren, demonstrating heredity within a family.

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Chromosome Noun

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[kroh-muh-sohm]

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Chromosome

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A thread-like structure of nucleic acids and protein found in the nucleus, carrying genetic information in the form of genes.

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Example: This diagram shows that a chromosome is a structure found inside a cell's nucleus and is made of tightly coiled DNA.

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Gene Noun

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[jeen]

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Gene

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A specific sequence of nucleotides in DNA that is located on a chromosome and codes for a functional product.

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Example: This diagram shows that a gene is a specific section of a DNA molecule, which is tightly coiled to form 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 arise by mutation and are found at the same place on a chromosome.

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Example: This image shows alleles are different forms of a gene, like 'A' and 'a', found on matching chromosomes, creating homozygous or heterozygous genotypes.

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Homozygous Adjective

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[hoh-moh-zy-guhs]

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Homozygous

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Having two identical alleles for a particular gene, inherited from both parents.

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

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Heterozygous Adjective

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[het-er-oh-zy-guhs]

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Heterozygous

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Having two different alleles for a particular gene, one inherited from each parent.

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Example: This diagram shows a pair of homologous chromosomes with different versions (alleles) of a gene, labeled 'A' and 'a', representing a heterozygous genotype.

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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 produces the same phenotype whether its paired allele is identical or different.

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Example: This Punnett square shows that when a dominant allele for brown eyes (B) is present, it masks the recessive allele for blue eyes (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 that produces its characteristic phenotype only when its paired allele is identical.

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Example: This diagram shows a recessive allele (lowercase 'b') on a chromosome, contrasting it with a dominant allele ('B') to explain genetic pairs.

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Genotype Noun

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[jee-noh-typ]

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Genotype

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The specific combination of alleles that constitutes the genetic makeup of an individual organism.

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Example: This image shows that a genotype is the specific combination of alleles (represented by letters like B and b) an organism has for a gene.

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Phenotype Noun

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[fee-noh-typ]

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Phenotype

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

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Example: This image shows that a phenotype is an organism's observable trait, like the different beak shapes of these finches, which are adapted for eating different foods.