{"id":10362,"date":"2026-07-03T17:39:42","date_gmt":"2026-07-03T17:39:42","guid":{"rendered":"https:\/\/kapdec.com\/help\/?p=10362"},"modified":"2026-07-03T17:39:42","modified_gmt":"2026-07-03T17:39:42","slug":"non-mendelian-genetics","status":"publish","type":"post","link":"https:\/\/kapdec.com\/help\/non-mendelian-genetics\/","title":{"rendered":"Non-mendelian Genetics"},"content":{"rendered":"
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KAPDEC® | Elite STEM Learning Platform | https:\/\/kapdec.com<\/a><\/p>\n

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Unit (5): Heredity<\/strong><\/h1>\n

Chapter: Non-mendelian genetics<\/strong><\/h2>\n

Reference:<\/em><\/strong> Non-Mendelian genetics, Types of non-mendelian inheritance, Codominance, Incomplete dominance, Multiple alleles, A polygenic trait, Polygenic inheritance, Lethal or lethal genes, Extracellular inheritance<\/em><\/p>\n

Learning objectives<\/strong><\/p>\n

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  • To understand about the types of non-mendelian inheritance<\/li>\n
  • To learn about polygenic inheritance, lethal genes, and extracellular inheritance<\/li>\n<\/ul>\n

    Non-Mendelian genetics<\/strong><\/p>\n

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    • Non-mendelian genetics involves the pattern of inheritance that does not follow Mendel’s laws.<\/li>\n
    • It describes the inheritance of traits linked to a single gene on chromosomes. When scientists began exploring more and more test crosses, they observed that there are several traits that do not match up with Mendel’s laws.<\/li>\n<\/ul>\n

      Types of non-mendelian inheritance<\/strong><\/p>\n

      Codominance <\/strong>-happens when both the alleles get expressed equally in the heterozygote phenotype.<\/p>\n

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      • The phenotype of the offspring is a combination of the phenotype of the parents. Thus, the trait is neither dominant nor recessive.<\/li>\n
      • exemplified by a plant that bears flowers with two distinct colour phenotypes.<\/li>\n
      • For instance, a white-spotted red flower could be caused by a cross between a red flower and a white flower. The alleles for the red and white colour phenotypes mean that they are codominant.<\/li>\n<\/ul>\n

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        Source: Kapdec.com<\/p>\n<\/div>\n

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        Incomplete dominance<\/strong> is a form of gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype.<\/p>\n

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        • It is also known as partial dominance.<\/li>\n
        • For e.g., in roses, the allele for red colour is dominant over the allele for white colour.<\/li>\n<\/ul>\n

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          Source: Kapdec.com<\/p>\n<\/div>\n

          Multiple alleles<\/strong> are located on homologous chromosomes on the equal locus.<\/p>\n

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          • When there are, three or more kinds of genes located on the same locus in a chromosome, they are called multiple alleles.<\/li>\n
          • An excellent example of multiple allele inheritance is human blood type. Blood type exists as four possible phenotypes: A, B, AB, & O. There are 3 alleles for the gene that determines blood type.<\/li>\n<\/ul>\n

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            Source: Kapdec.com<\/p>\n<\/div>\n

            A polygenic trait<\/strong> is a characteristic, such as height or skin colour, that is influenced by two or more genes.<\/p>\n

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            • Because multiple genes are involved, polygenic traits do not follow the patterns of Mendelian inheritance.<\/li>\n
            • Many polygenic traits are also influenced by the environment and are called multifactorial.<\/li>\n<\/ul>\n

              Polygenic inheritance<\/strong> refers to the inheritance of a trait governed by more than one gene.<\/p>\n

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              • Generally, three or more genes govern the inheritance of polygenic traits. Multiple independent genes have an additive or similar effect on a single quantitative trait.<\/li>\n
              • \u00a0In humans, height, skin colour, hair colour, and eye colour are examples of polygenic traits. Type-2 diabetes, coronary heart disease, cancer, and arthritis are also deemed polygenic.<\/li>\n
              • However, these conditions are not just genetic since polygenes can be influenced by environmental factors.<\/li>\n<\/ul>\n

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                Source: Kapdec.com<\/p>\n<\/div>\n

                Lethal or lethal genes<\/strong> or lethal alleles are alleles causing the end of an entity which carries it.<\/p>\n

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                • Basically, lethal genes are lethal to the organism carrying it, lethal meaning (here) death.<\/li>\n
                • Typically, it is the consequence of gene-mutation that is required to grow and develop.<\/li>\n<\/ul>\n

                  Extracellular inheritance<\/strong> is a non-Mendelian inheritance wherein a trait was transmitted from the parent to the offspring not nuclear in nature but involving other organellar genetic material.<\/p>\n

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                  • There are traits manifested in certain eukaryotes that result from extranuclear inheritance. The mitochondria, for instance, contain genetic material independent of the chromosomes inside the nucleus.<\/li>\n<\/ul>\n

                    Solved examples<\/strong><\/p>\n

                    Example 1.<\/strong> In butterfly bushes, dark purple and pink parents will produce offspring with lavender flowers. This is a result of<\/p>\n

                    a) codominance b) incomplete dominance<\/p>\n

                    c)complete dominance d) recessive dominance<\/p>\n

                    Solution 1:<\/strong> b. In butterfly bushes, dark purple and pink parents will produce offspring with lavender flowers. This is a result of incomplete dominance<\/p>\n

                    Example 2.<\/strong> Which term(s) best describes the inheritance of human blood types?<\/p>\n

                    a) incomplete dominance and multiple alleles<\/p>\n

                    b) codominance and epistasis<\/p>\n

                    c)codominance and multiple alleles<\/p>\n

                    d)incomplete dominance and codominance<\/p>\n

                    Solution 2:<\/strong> c. the inheritance of human blood types best describes about co dominance and multiple alleles.<\/p>\n

                    \u00a0Summary \u00a0<\/strong><\/p>\n

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                    • Non-mendelian genetics involves the pattern of inheritance that does not follow Mendel’s laws.<\/li>\n
                    • Codominance -happens when both the alleles get expressed equally in the heterozygote phenotype.<\/li>\n
                    • Incomplete dominance is a form of gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype.<\/li>\n
                    • Multiple alleles are located on homologous chromosomes on the equal locus.<\/li>\n
                    • A polygenic trait is a characteristic, such as height or skin colour, that is influenced by two or more genes.<\/li>\n
                    • Polygenic inheritance refers to the inheritance of a trait governed by more than one gene.<\/li>\n
                    • Lethal or lethal genes or lethal alleles are alleles causing the end of an entity which carries it.<\/li>\n
                    • Extracellular inheritance is a non-Mendelian inheritance wherein a trait was transmitted from the parent to the offspring not nuclear in nature but involving other organellar genetic material.<\/li>\n<\/ul>\n

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