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Definition:
An alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. For example, the gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r).
Related Terms
• Genes
• Heterozygous
• Homozygous
Organisms have two alleles for each trait. When the alleles of a pair are heterozygous, one is dominant and the other is recessive. The dominant allele is expressed and the recessive allele is masked. Using the previous example, round seed shape (R) is dominant and wrinkled seed shape (r) is recessive. Round: (RR) or (Rr), Wrinkled: (rr).
Chromosomes and Gender
Chromosomes are long, stringy aggregates of genes that carry heredity information. Gender is determined by the presence or absence of certain chromosomes.
Law of Segregation
The principles that govern heredity were discovered by a monk named Gregor Mendel in the 1860's. One of these principles is now called Mendel's law of segregation.
Independent Assortment
This principle of heredity formulated by Gregor Mendel states that traits are transmitted to offspring independently of one another.
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Allele
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