<P> The concept of dominance was introduced by Gregor Johann Mendel . Though Mendel , `` The Father of Genetics '' , first used the term in the 1860s , it was not widely known until the early twentieth century . Mendel observed that , for a variety of traits of garden peas having to do with the appearance of seeds , seed pods , and plants , there were two discrete phenotypes , such as round versus wrinkled seeds , yellow versus green seeds , red versus white flowers or tall versus short plants . When bred separately , the plants always produced the same phenotypes , generation after generation . However , when lines with different phenotypes were crossed ( interbred ) , one and only one of the parental phenotypes showed up in the offspring ( green , or round , or red , or tall ) . However , when these hybrid plants were crossed , the offspring plants showed the two original phenotypes , in a characteristic 3 : 1 ratio , the more common phenotype being that of the parental hybrid plants . Mendel reasoned that each parent in the first cross was a homozygote for different alleles ( one parent AA and the other parent aa ) , that each contributed one allele to the offspring , with the result that all of these hybrids were heterozygotes ( Aa ) , and that one of the two alleles in the hybrid cross dominated expression of the other : A masked a . The final cross between two heterozygotes ( Aa X Aa ) would produce AA , Aa , and aa offspring in a 1 : 2 : 1 genotype ratio with the first two classes showing the ( A ) phenotype , and the last showing the ( a ) phenotype , thereby producing the 3 : 1 phenotype ratio . </P>
<P> The concept of dominance was introduced by Gregor Johann Mendel . Though Mendel , `` The Father of Genetics '' , first used the term in the 1860s , it was not widely known until the early twentieth century . Mendel observed that , for a variety of traits of garden peas having to do with the appearance of seeds , seed pods , and plants , there were two discrete phenotypes , such as round versus wrinkled seeds , yellow versus green seeds , red versus white flowers or tall versus short plants . When bred separately , the plants always produced the same phenotypes , generation after generation . However , when lines with different phenotypes were crossed ( interbred ) , one and only one of the parental phenotypes showed up in the offspring ( green , or round , or red , or tall ) . However , when these hybrid plants were crossed , the offspring plants showed the two original phenotypes , in a characteristic 3 : 1 ratio , the more common phenotype being that of the parental hybrid plants . Mendel reasoned that each parent in the first cross was a homozygote for different alleles ( one parent AA and the other parent aa ) , that each contributed one allele to the offspring , with the result that all of these hybrids were heterozygotes ( Aa ) , and that one of the two alleles in the hybrid cross dominated expression of the other : A masked a . The final cross between two heterozygotes ( Aa X Aa ) would produce AA , Aa , and aa offspring in a 1 : 2 : 1 genotype ratio with the first two classes showing the ( A ) phenotype , and the last showing the ( a ) phenotype , thereby producing the 3 : 1 phenotype ratio . </P>
who came up with dominant and recessive traits
who came up with dominant and recessive traits
Gregor Johann Mendel
Gregor Johann Mendel