The main difference between monogenic and polygenic inheritance is that in monogenic inheritance, a single gene determines a single trait whereas, in polygenic inheritance, two or more genes are involved in the determination of a particular trait.
Monogenic and polygenic inheritance are two types of inheritance by which offspring get genetic information from their parents. According to Mendelian genetics, each gene has two alleles that determine the character, and these alleles segregate independently during gamete formation to produce a distinct character.
Key Areas Covered
- What is Monogenic Inheritance
- Definition, Characteristics, Importance
- What is Polygenic Inheritance
- Definition, Characteristics, Importance
- Similarities Between Monogenic and Polygenic Inheritance
- Outline of Common Features
- Difference Between Monogenic and Polygenic Inheritance
- Comparison with Key Differences
Key Terms
Inheritance, Monogenic Inheritance, Polygenic Inheritance
What is Monogenic Inheritance
Monogenic inheritance is the determination of a character by a single gene. Here, the two alleles of a single locus determine the trait. However, it is a form of mendelian inheritance in which the independent segregation of alleles allows the determination of the trait. During gamete formation, each of the two alleles segregates into separate garments according to the first law of Mendelian inheritance. According to the law of independent assortment, the second law of Mendelian inheritance, these alleles assort independently to produce the F1 generation. Finally, according to the law of dominance, the third law of Mendelian inheritance, dominant alleles and recessive alleles co-work to determine the trait. Usually, sickle cell anemia, Huntington’s disease, and cystic fibrosis are monogenic traits.
Figure 1: Cystic Fibrosis Inheritance
Furthermore, there are two stages of alleles to express the monogenic trait. Some monogenic traits are autosomal dominant such as Huntington’s disease while others are autosomal recessive traits. In the dominant traits, the trait is expressed in the presence of the dominant alleles while in the recessive traits, the trait is expressed when both alleles are recessive. For instance, sickle cell anemia and cystic fibrosis are recessive traits.
What is a Polygenic Inheritance
Polygenic inheritance is the determination of a single character by two or more genes. Here, the contributing genes show incomplete dominance. While being a mixture of parental traits, environmental factors also affect polygenic inheritance. On the other hand, polygenic traits are always quantitative. In addition, polygenic traits exhibit a continuous distribution in a population. Thus, the distribution curve of the polygenic inheritance is bell-shaped. Usually, great variability of genotypes occurs within a population in polygenic traits. The organisms at the middle of the distribution curve consist of a combination of both dominant and recessive alleles. Individuals with many of the dominant alleles or recessive alleles may appear at the end of the curve.
Figure 2: Skin Color Determination
The color of the human eye is controlled by 16 different genes. The eye color is determined by the amount of melanin produced in front of the iris. The color can be black, brown, green, hazel, or blue. The skin color of humans is another example of polygenic inheritance. The color of the skin is determined by the amount of melanin produced in the skin. When the number of dark alleles present in the skin is high, the color of the skin becomes darker.
Similarities Between Monogenic and Polygenic Inheritance
- Monogenic and polygenic inheritance are two types of inheritance that follow Mendelian genetics.
- Genes determine traits of a particular character.
- A particular gene has two alleles that segregate independently during gamete formation to produce a distinct character.
Difference Between Monogenic and Polygenic Inheritance
Definition
Monogenic inheritance refers to the inheritance that is controlled by the alleles for one particular locus while polygenic inheritance refers to the kind of inheritance in which the trait is produced from the cumulative effects of many genes.
Number of Genes
Usually, in monogenic inheritance, a single gene determines a particular character while in polygenic inheritance, two or more genes determine a particular character.
Type of Character
Monogenic inheritance determines qualitative characters while polygenic inheritance determines quantitative characters.
Examples
Some of the characters monogenic inheritance include sickle cell anemia, Huntington’s disease, and cystic fibrosis while some examples of polygenic inheritance are skin pigmentation, height, and eye color.
Mendelian Inheritance
Monogenic inheritance is a type of Mendelian inheritance while polygenic inheritance is a non-Mendelian inheritance.
Conclusion
In brief, monogenic inheritance is the determination of a particular character by a single gene while polygenic inheritance is the determination of a particular character by two or more genes. In addition, monogenic inheritance determines qualitative characters while polygenic inheritance determines quantitative characters. Some examples of monogenic inheritance are sickle cell anemia, Huntington’s disease, and cystic fibrosis while examples of polygenic inheritance are skin pigmentation, height, and eye color. Therefore, the main difference between monogenic and polygenic inheritance is the number of genes that determines a particular character.
References:
- (2021, July 28). Monogenic inheritance. Biology Articles, Tutorials & Dictionary Online. Retrieved September 6, 2022.
- (2022, June 16). Polygenic inheritance – definition and examples – biology online dictionary. Biology Articles, Tutorials & Dictionary Online. Retrieved September 6, 2022.
Image Courtesy:
- “2926 Autosomal Recessive Inheritance-new” By OpenStax College- Own Work (CC-BY 3.0) via Commons Wikimedia
- “Human skin colour chart & histogram” By CKRobinson – Own Work (CC By SA-4.0) via Commons Wikimedia
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