Genetics and Punnett Squares Review

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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 mechanisms by which traits are passed from parents to their offspring.

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Example: This diagram shows that cells contain a nucleus with chromosomes, which are made of DNA, and that specific segments of DNA are called genes.

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Heredity Noun

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[huh-red-i-tee]

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Heredity

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The biological process of passing genetic information and physical or mental characteristics from one generation to another.

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Example: This pedigree chart shows how a specific trait, represented by the red color, is passed down from parents to their children through multiple generations.

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Trait Noun

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[trayt]

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Trait

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A specific, genetically determined characteristic or quality belonging to an organism, such as eye color or height.

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Example: This diagram shows that a trait, like eye color, is an observable characteristic determined by underlying biological factors, such as the amount of pigment in cells.

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DNA Noun

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[dee-en-ay]

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DNA

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Deoxyribonucleic acid, a self-replicating molecule carrying the genetic instructions for the development and function of all organisms.

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Example: This image shows the DNA double helix, made of a sugar-phosphate backbone and rungs of paired bases: Adenine with Thymine, and Guanine with Cytosine.

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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 serves as the basic physical and functional unit of heredity.

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Example: This diagram shows that a gene is a specific section of a long DNA molecule, which is tightly 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 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 diagram shows alleles (A and a) as different versions of a gene on homologous chromosomes, forming homozygous (AA, aa) or heterozygous (Aa) pairs.

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Mutation Noun

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[myoo-tay-shun]

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Mutation

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A permanent alteration in the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA.

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Example: A change (mutation) in a gene's DNA sequence can cause the cell to produce an abnormal protein, which can lead to a different trait.

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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 that an individual organism possesses for a particular genetic trait.

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Example: This image shows that a genotype is the specific pair of alleles (letters like B and b) an organism has for a trait, located on its chromosomes.

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Phenotype Noun

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[fee-noh-type]

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Phenotype

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The set of observable physical or behavioral characteristics of an individual resulting from its genotype and the environment.

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Example: This image shows that an organism's genotype (the DNA) provides the instructions that result in its phenotype (its observable physical traits).

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Dominant Allele Noun

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[dom-uh-nunt 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 in a heterozygous pair.

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Example: This Punnett square shows that when the brown eye allele (B) is present, it masks the blue eye allele (b), resulting in brown eyes, making the 'B' allele dominant.