Polygenic Traits
Polygenic traits are different physical characteristics of individuals, due to specific inheritance patterns. It is responsible for difference in phenotypic makeup of individuals. Physical appearance of individuals is determined by genotypic ratio and chromosomal inheritance. This phenomenon was put forth by Mendel, popularly known as 'Mendel's Laws of Inheritance'. In case of polygenic traits, the characteristic features of individual result from interaction of different genes. In layman's language, we can exemplify with an individual having high blood pressure. High blood pressure does not result due to activity of single gene. This particular phenotype is the net result of interaction of cholesterol genes, obesity genes, transporter genes and addictive genes. The combined effect of these multiple genes or polygenes, is the reason behind high blood pressure. That was an elementary approach of polygenic traits. You might also like to read more on interesting aspects of human genetics.
Genetic Phenomenon of Polygenic Traits
Polygenic traits is not only observed in human beings but are also present in animals, birds, insects, flies etc. In terms of human genetics, polygenic traits is defined as, inherited characteristics when two or more genes are involved in determining the phenotype of individuals. Thus, the cumulative effects of genes are responsible for determining many traits like, weight, height, shape, color and metabolic rate of individuals. They characteristics of polygenic traits are:
Polygenic traits do not follow Mendel's patterns of inheritance.
They are recognized by their expressions that result from gradation of continuous variation.
Additive effects of two or more separate pair of genes control continuous variation.
The traits are quantified by measuring the variation, rather than counting.
The phenotypic expression vary in wider range as a result of contributing pairs of genes.
Polygenic traits are also known as quantitative traits or multifactorial traits. To understand these synonyms, you need to understand the mechanism of genetic inheritance. Polygenic traits are controlled by two or more genes at different loci on different chromosomes or it is the trait that is controlled by non-allelic genes. They are known as quantitative traits as their phenotypic expression is dependent on multiple alleles located on different chromosomes. You might also like to read about genetic drift.
The quantitative aspect (e.g how tall or how short) or phenotype of the individual is represented as trait value. When frequency of individuals with polygenic traits is plotted against trait value, the graph is bell shaped. Polygenic traits are result of additive effects of contribution of each genes in loci and therefore they do not follow typical dominance and recessive patterns. The second aspect of polygenic genes are, the traits are determined by environmental variations. It means that an individual can be genetically same, but can differ in their physical appearance, while rest are congenial disorders. Polygenic traits can be determined by knowing the number of quantitative trait loci, that plays an important role in determining the genetic architecture of an individual. Read more on genetic disorders in humans.
Examples of Polygenic Traits in Humans
Examples of polygenic traits, governed by environmental factors are:
Weight
Height
Eye color
Intelligence
Behavior
Skin color
Polygenic traits examples with disorders in genetic components are:
Cleft palate
Cancer
Diabetes
Autism
Congenital heart disease
Congenital dislocation of hip
Talipes
Pyloric stenosis
Neural tube defects
Schizophrenia
Diabetes Mellitus
Glaucoma
Hypertension
Manic depression
Ischaemic heart disease
Maniac depression
Eczema
Dermatitis
Spina bifida
Anencephaly
Read more on:
Understanding Genes
Facts about Human Chromosomes
Polygenic traits is an important genetic phenomenon, governing different variations and characteristic in individuals. Polygenic traits in humans are interesting to study and observe.
NOTE
Glossary of Terms
Genes: Unit of heredity in a living organism.
Chromosomes: Organized structure of DNA and protein that embeds genes.
Alleles: Different forms of genes in a single genetic locus.
Genetic Locus: Specific location of gene or DNA sequence in chromosome.
Phenotype: Observable characteristics, morphology, physiological properties of an organism
Genotype: Information in genes that determines the phenotypic traits.
Quantitative Trait Locus (QTL): Region of DNA, found in different chromosomes, associated with a particular phenotypic trait.
Polygenic traits are different physical characteristics of individuals, due to specific inheritance patterns. It is responsible for difference in phenotypic makeup of individuals. Physical appearance of individuals is determined by genotypic ratio and chromosomal inheritance. This phenomenon was put forth by Mendel, popularly known as 'Mendel's Laws of Inheritance'. In case of polygenic traits, the characteristic features of individual result from interaction of different genes. In layman's language, we can exemplify with an individual having high blood pressure. High blood pressure does not result due to activity of single gene. This particular phenotype is the net result of interaction of cholesterol genes, obesity genes, transporter genes and addictive genes. The combined effect of these multiple genes or polygenes, is the reason behind high blood pressure. That was an elementary approach of polygenic traits. You might also like to read more on interesting aspects of human genetics.
Genetic Phenomenon of Polygenic Traits
Polygenic traits is not only observed in human beings but are also present in animals, birds, insects, flies etc. In terms of human genetics, polygenic traits is defined as, inherited characteristics when two or more genes are involved in determining the phenotype of individuals. Thus, the cumulative effects of genes are responsible for determining many traits like, weight, height, shape, color and metabolic rate of individuals. They characteristics of polygenic traits are:
Polygenic traits do not follow Mendel's patterns of inheritance.
They are recognized by their expressions that result from gradation of continuous variation.
Additive effects of two or more separate pair of genes control continuous variation.
The traits are quantified by measuring the variation, rather than counting.
The phenotypic expression vary in wider range as a result of contributing pairs of genes.
Polygenic traits are also known as quantitative traits or multifactorial traits. To understand these synonyms, you need to understand the mechanism of genetic inheritance. Polygenic traits are controlled by two or more genes at different loci on different chromosomes or it is the trait that is controlled by non-allelic genes. They are known as quantitative traits as their phenotypic expression is dependent on multiple alleles located on different chromosomes. You might also like to read about genetic drift.
The quantitative aspect (e.g how tall or how short) or phenotype of the individual is represented as trait value. When frequency of individuals with polygenic traits is plotted against trait value, the graph is bell shaped. Polygenic traits are result of additive effects of contribution of each genes in loci and therefore they do not follow typical dominance and recessive patterns. The second aspect of polygenic genes are, the traits are determined by environmental variations. It means that an individual can be genetically same, but can differ in their physical appearance, while rest are congenial disorders. Polygenic traits can be determined by knowing the number of quantitative trait loci, that plays an important role in determining the genetic architecture of an individual. Read more on genetic disorders in humans.
Examples of Polygenic Traits in Humans
Examples of polygenic traits, governed by environmental factors are:
Weight
Height
Eye color
Intelligence
Behavior
Skin color
Polygenic traits examples with disorders in genetic components are:
Cleft palate
Cancer
Diabetes
Autism
Congenital heart disease
Congenital dislocation of hip
Talipes
Pyloric stenosis
Neural tube defects
Schizophrenia
Diabetes Mellitus
Glaucoma
Hypertension
Manic depression
Ischaemic heart disease
Maniac depression
Eczema
Dermatitis
Spina bifida
Anencephaly
Read more on:
Understanding Genes
Facts about Human Chromosomes
Polygenic traits is an important genetic phenomenon, governing different variations and characteristic in individuals. Polygenic traits in humans are interesting to study and observe.
NOTE
Glossary of Terms
Genes: Unit of heredity in a living organism.
Chromosomes: Organized structure of DNA and protein that embeds genes.
Alleles: Different forms of genes in a single genetic locus.
Genetic Locus: Specific location of gene or DNA sequence in chromosome.
Phenotype: Observable characteristics, morphology, physiological properties of an organism
Genotype: Information in genes that determines the phenotypic traits.
Quantitative Trait Locus (QTL): Region of DNA, found in different chromosomes, associated with a particular phenotypic trait.
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