Dominant alleles are always expressed in the organism, while recessive traits tend to be expressed only when the dominant allele is not present. The relationship between dominant and recessive genes is described by the Law of Segregation. As related by About.com, Gregor Mendel observed nine different traits among his pea plants and found that certain traits, such as pod color, bred true only when two recessive alleles were present.Know More
Sexually reproducing organisms carry two copies of each gene in their DNA. When these two copies are the same, or "homozygous," their effect is to produce whatever trait the genes are identified with. When different versions of the gene are paired, however, what usually happens is that one gene is expressed at the expense of the other. The expressed trait is then described as dominant.
By carefully isolating nine separate traits in his pea plants, Mendel was able to show that each trait--such as plant height and pod color--bred true in self-fertilized plants. When the plants were cross-fertilized, however, their traits did not blend; tall and short plants didn't produce medium-height plants, for example. Instead, according to Genome.gov, three out of four offspring were tall. In this case, tall was a dominant allele.Learn more about Molecular Biology & DNA
An organism's genotype is the entire set of genes that it carries in its genome, and its phenotype is the observable effect of those genes on the body and behavior of the organism. Biologists draw a distinction between genotypes and phenotypes to clarify the difference between an organism's genetic heritage and the effects that its combination of genes has.Full Answer >
The terms "dominant" and "recessive" are used to describe the phenotypic expression of certain traits or characteristics an individual possesses and not the genes themselves. In humans, each gene has two copies, or alleles. A person with a dominant allele for a specific trait always expresses that trait, even if the other copy of the allele he possesses is recessive. Dominant alleles repress, or mask, recessive alleles.Full Answer >
Freckles are a dominant trait. Freckles come from genes and the sun and are most often seen on people with light-colored skin.Full Answer >
Traits that are linked to alleles can be either homozygous or heterozygous, according to the Genetics Home Reference at the National Institutes of Health. These are also known as recessive and dominant traits, respectively.Full Answer >