Non-Mendelian

Non-Mendelian inheritance is a general term that refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent contributes one of two possible alleles for a trait. If the two alleles are different, the dominant allele will be expressed, while the effect of the other allele, called recessive, is masked. In non-Mendelian inheritance, traits are not determined by dominant alleles and can involve more than one gene.

Types of Non-Mendelian Inheritance

Non-Mendelian inheritance includes a variety of inheritance patterns that do not follow the basic Mendelian pattern. These include:

• Codominance: In codominance, both alleles for a gene are expressed in the heterozygote. This results in phenotypes that are a combination of both alleles. An example of codominance is the ABO blood group system in humans.

• Incomplete dominance: In incomplete dominance, the phenotype of the heterozygote is intermediate between the phenotypes of the homozygote. This is seen in the four o'clock plant, where pink flowers are produced by plants with one red allele and one white allele.

• Multiple alleles: In some cases, there are more than two possible alleles for a gene. This is seen in the ABO blood group system in humans, where there are three possible alleles: A, B, and O.

• Polygenic inheritance: Polygenic inheritance involves multiple genes affecting a trait. This is seen in human traits such as height and skin color.

• Sex-linked inheritance: Sex-linked inheritance involves genes located on the sex chromosomes. This is seen in traits such as color blindness and hemophilia in humans.

See also

• Mendelian inheritance
• Genetics
• Gene
• Allele
• Chromosome

References

Non-Mendelian Resources
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