Question

Define the term epigenetic inheritance, and describe two examples.

Short answer

Epigenetic inheritance refers to the passing on of gene expression changes from parents to offspring, not through changes in the genes themselves, but their expression. An example is the variation in the Agouti mouse's fur color and weight, which is dependent on the expression of their agouti gene. Another example is the influence of environment on gene expression, as seen in the Dutch Hunger Winter where nutritional scarcity in pregnant women led to health problems in their offspring.

Step-by-step solution

Defining Epigenetic Inheritance

Epigenetic inheritance is a process where changes in gene expression can be passed down from parents to offspring without alterations to the genetic code itself. In other words, the genes do not change, but how they are expressed (turned 'on' or 'off') does. It involves distinct changes to the phenotype without any modifications to the genotype.

First Example of Epigenetic Inheritance

One known example of this is the manner in which the Agouti mouse's fur color is determined. Some Agouti mice have yellow fur and a propensity towards obesity, while others have brown fur and a normal weight, but both types have identical genetic codes. What's different is the expression of their agouti gene, which is influenced by an epigenetic factor (methyl groups). White-furred, obese mice have a fewer number of attached methyl groups, which leads to higher agouti gene expression resulting in the observed traits.

Second Example of Epigenetic Inheritance

Epigenetic inheritance is, moreover, evident in humans. One example of this is the Dutch Hunger Winter that occurred during World War II. During the famine, pregnant women unable to access adequate nutrition gave birth to children who, later in life, had higher rates of health problems such as obesity and mental disorders. These health problems were not due to genetic changes but the epigenetic changes in gene expression stimulated by the environment (nutrition scarcity).