Complex Pattern of Inheritance

Angelina Khang

Multiples Alleles

Definition :Traits are controlled by more alternative forms of a gene that can occupy the same locus.


Offspring phenotype : The more alleles you have the more gene combination are possible. One allele for the trait was dominant and prevents the other, recessive, allele from being expressed


Example : gene of the ABO blood group system - Found on platelets, epithelium, and cells other than erythrocytes, AB antigens (as with other serotypes) can also cause an adverse immune response to organ transplantation.

human- leukocyte-associated antigen (HLA) genes- controlled by genes located on chromosome 6.

Incomplete Dominance

Definition : neither allele is completely dominant over the other allele.


Offspring phenotype : a mixture or blending of the two


Example : A snapdragon flower that is pink as a result of cross-pollination between a red flower and a white flower when neither the white or the red alleles are dominant.

  • A child with wavy hair as a result of one parent's curly hair and the other's straight hair.
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    Codominance

    Definition : relationship between two versions of a gene.


    Offspring phenotype : both traits are expressed equally.


    Example : chicken and roan horse

    Polygenic Traits

    Definition : one whose phenotype is influenced by more than one gene.


    Offspring phenotype : Patterns of inheritance that can be measured quantitatively


    Example : human skin color and height