recressive

Recessive refers to a gene or a trait that is expressed only when two copies of the gene are present. In genetics, individuals inherit two alleles for each gene, one from each parent. If an individual inherits two different alleles for a particular gene, one dominant and one recessive, the dominant allele will determine the expressed trait. The recessive allele will be present but its effect will be masked by the dominant allele. Only when an individual inherits two copies of the recessive allele will the recessive trait be expressed. For example, in pea plants, the allele for wrinkled seeds is recessive, while the allele for smooth seeds is dominant. A plant with one allele for smooth seeds and one for wrinkled seeds will have smooth seeds because the smooth allele is dominant. However, a plant with two alleles for wrinkled seeds will have wrinkled seeds because there is no dominant allele to mask the recessive trait. This concept is fundamental to understanding Mendelian inheritance patterns and how genetic variations are passed down through generations. The term is commonly used in discussions of genetic disorders, where carrier individuals may have one dominant and one recessive allele and thus not show the trait themselves but can pass the recessive allele to their offspring.