The Impact of Environment on Gene Expression

Gene expression is not only dependent on genotype but also influenced by the environment. The environment affects gene expression by regulating gene activity, leading to changes in phenotype.

1. Qualitative and Quantitative Traits

• Qualitative traits: Traits that are expressed in a qualitative way, often less dependent on environmental conditions. Examples include flower color, blood type, eye color, fruit shape, etc.

• Quantitative traits: Traits that are expressed in a quantitative way, often have a broad range of response and depend on environmental conditions. Examples include plant height, milk yield, number of eggs, etc.

Note:

• The distinction between qualitative and quantitative traits may not always be clear-cut. For example, fruit color can be affected by light, temperature, etc.

• Some traits may be considered qualitative in one species but quantitative in another.

2. The Reaction Norm of a Gene

The reaction norm of a gene is the range of variation of a genotype corresponding to different environmental conditions. The reaction norm is represented by the set of phenotypes that can appear from a given genotype in different environmental conditions.

Example:

• Rice with genotype A can yield from 5 tons/ha to 8 tons/ha depending on environmental conditions such as soil, water, fertilizer, etc.

• Humans with genotype B can be from 1m60 to 1m80 tall depending on diet, exercise, etc.

Note:

• The reaction norm of a gene is a genetic characteristic, determined by the genotype.

• The reaction norm of a gene is relative, meaning it has certain limits.

• The reaction norm of a gene can change over time, depending on changes in the environment.

3. Phenotypic Plasticity

Phenotypic plasticity is the phenomenon where one genotype can produce different phenotypes in response to different environmental conditions. Phenotypic plasticity is the change in phenotype that is not related to changes in DNA sequence.

Example:

• Cotton plants grown in arid regions have smaller leaves than those grown in humid regions.

• Manual laborers tend to have more developed muscles than office workers.

Note:

• Phenotypic plasticity is a non-heritable genetic phenomenon.

• Phenotypic plasticity is a reversible phenomenon, meaning that the phenotype changes in a direction that is beneficial for the organism to adapt to the environment.

4. Characteristics of Phenotypic Plasticity

• Physiological self-regulation: Phenotypic plasticity is a manifestation of physiological self-regulation that helps organisms adapt to changes in the environment.

• The degree of plasticity depends on the genotype: Each genotype has the ability to adjust its phenotype within a certain range. For example, some plant species can tolerate drought better than others.

Conclusion:

The impact of the environment on gene expression is a common phenomenon in nature. Understanding the impact of the environment on gene expression is essential for applying genetics to production, animal husbandry, and medicine.

Note:

• The environment affects gene expression but does not change the genotype.

• The impact of the environment on gene expression is relative, depending on the specific genotype and environment.

• Understanding the impact of the environment on gene expression is the basis for applying genetics in practice.