Polygenic Inheritance - Characteristics, Examples in Plants and Humans

Polygenic Inheritance: Inheritance is the biological process through which offspring acquire specific traits from their parents. Characteristics like height, skin pigmentation, eye color, and hair color are examples of polygenic inheritance, where the interaction of multiple genes determines these traits. These genes, known as alleles, are inherited from parents and can have an additive or similar effect on a single trait.

Sexual Reproduction in Flowering Plants

Polygenic Inheritance

Free Study Material for NEET Preparation

Polygenic Inheritance Characteristics

• Involvement of multiple genes: Numerous genes contribute to the expression of the trait. Each gene's impact is generally minor, but together, they determine the final phenotype.
• Additive effects: Alleles of each gene tend to have an additive effect on the phenotype. This means that the effects of alleles from both parents are cumulatively considered. For instance, if a gene has alleles for tallness and shortness, an individual inheriting two tallness alleles will be taller than someone with one tallness and one shortness allele.
• Continuous variation: Polygenic traits exhibit a continuum of phenotypic variation due to the additive effects of multiple genes. This results in a range of possible phenotypes, rather than distinct categories. For example, human height varies from very short to very tall.
• Environmental influence: Apart from genetic factors, environmental conditions can also influence polygenic traits. For instance, nutrition can impact height, while sun exposure can affect skin colour.

Explore - NEET Online Courses by PW

How Do Polygenic Diseases Occur?

Polygenic Inheritance Examples

1. Human Skin Colour: The wide range of human skin tones is a manifestation of polygenic inheritance. Multiple genes influence the production of melanin, the pigment responsible for skin colour, leading to the diversity of skin tones observed in human populations.
2. Height: Polygenic inheritance also plays a role in determining an individual's height. Multiple genes contribute to the development of skeletal structures and growth patterns, resulting in the variation in height seen among individuals.
3. Eye Colour: The colour of human eyes is determined by the interaction of several genes. The combination of these genes contributes to the diverse spectrum of eye colours observed in different individuals.
4. Hair Colour: Similarly, the colour of human hair is influenced by multiple genes. The interaction of these genes determines the specific shade of hair colour exhibited by an individual.
5. Susceptibility to Disease: Certain diseases, such as heart disease and diabetes, are influenced by polygenic factors. Multiple genes, in conjunction with environmental factors, contribute to an individual's predisposition to these diseases.

Female Gametophyte

Polygenic Inheritance in Humans

1. Height: Human height is influenced by multiple genes, with each gene contributing to a small portion of the overall height variation.
2. Skin Colour: The variation in human skin colour is controlled by multiple genes affecting the production of melanin, the pigment responsible for skin colour.
3. Intelligence: Intelligence is a complex trait influenced by multiple genes, with each gene contributing to different aspects of cognitive function.
4. Body Mass Index (BMI): BMI, a measure of body fat based on height and weight, is influenced by multiple genes controlling factors such as metabolism and appetite.

Vegetative Propagation

Polygenic Inheritance in Plants

1. Grain Yield: Multiple genes control traits such as tiller number, grain size, and plant height, influencing the yield of grains in crops like wheat, rice, or maize.
2. Plant Height: The height of a plant can be influenced by multiple genes, with each gene contributing to a small portion of the overall height variation.
3. Fruit Size: The size of fruits, such as in tomatoes or watermelons, is controlled by multiple genes affecting factors like cell division, expansion, and sugar content.
4. Leaf Size: The size of leaves in plants can be influenced by the interaction of multiple genes affecting cell growth and division.

1. Kernel Colour of Wheat: Wheat kernel colour is determined by three independently assorted pairs of alleles. Dark red wheat kernels result from the dominant allele AABBCC, while white kernels result from the recessive allele aabbcc. Crossing AABBCC wheat with aabbcc produces an F1 generation with red kernels intermediate to AaBbCc. In the F2 generation, one white kernel plant is produced for every 63 red kernel plants of various shades.
2. Corolla Length in Tobacco: The length of the tobacco plant's corolla is determined by five genes, leading to variation in corolla length due to polygenic inheritance.

Mendelian Inheritance vs. Polygenic Inheritance