récessives

Recessive refers to a type of gene, or more precisely, an allele, that only expresses its trait when two copies of it are present in an individual's genotype. In simpler terms, if an organism inherits one dominant allele and one recessive allele for a particular gene, the trait associated with the dominant allele will be observed. The recessive trait will only be visible if the organism inherits two copies of the recessive allele. This concept is fundamental to understanding Mendelian genetics, the study of heredity. For example, in pea plants, the allele for wrinkled seeds is recessive, while the allele for round seeds is dominant. A pea plant will have round seeds if it has at least one dominant allele, but it will only have wrinkled seeds if it has two recessive alleles for seed shape. The presence of a dominant allele masks the expression of a recessive allele. When discussing genotypes, an individual with two identical alleles (either two dominant or two recessive) is said to be homozygous for that gene. An individual with two different alleles (one dominant and one recessive) is called heterozygous. Only heterozygous individuals can carry a recessive allele without expressing its corresponding trait.