Introduction to Gene Expression and Epigenetics

Gene expression is a complex process that determines how genetic information is used in the development and function of living organisms. Contrary to popular belief from secondary school biology, the DNA sequence itself does not change in response to environmental factors. Instead, the way genes are expressed can be altered through epigenetic changes.

Simon Gregory, an associate professor of medical genetics and co-director of the Duke Epigenetics and Epigenomics Program, explains that while the sequence of DNA remains constant, environmental factors can influence how genes are expressed. Understanding these changes requires an appreciation of DNA as hardware, whereas gene expression is the software that controls various functions. This article explores the nuances of epigenetics and how it impacts gene expression.

Epigenetic Changes: Turning Genes On and Off

Epigenetics is the study of heritable changes in gene expression that do not involve alterations to the underlying DNA sequence. Environmental factors like food, drugs, and toxins can cause epigenetic changes by modifying how molecules bind to DNA or changing the structure of proteins that DNA wraps around. This process can alter gene activity in either a minor or major way, turning genes on when they should be off or vice versa.

These changes can be heritable, meaning they can be passed on from parent cell to daughter cell, as well as from parent to child. An example of this is seen in the survivors of the Dutch famine during World War II. Studies have revealed that the epigenetic changes caused by famine appeared not in the survivors themselves, but in their children and grandchildren. This unique insight into intergenerational effects suggests the adage should be modified to, "You are what your grandparents ate."

Understanding Heritability and Inheritance

Heritability in the context of epigenetics refers to the ability of these changes to be passed on to future generations. Unlike permanent genetic changes that alter DNA sequences, epigenetic modifications can be maintained and sometimes passed down. However, they are not always guaranteed to be inherited, as they depend on various factors within the cell environment.

The heritability of epigenetic changes means they can influence the traits of future generations. This has significant implications for understanding diseases and health outcomes. For example, understanding how epigenetic changes contribute to diabetes, cancer, and other conditions will help in developing targeted therapies and preventive measures.

Can Viruses and Bacteria Evolve Resistance to Vaccines and Medications?

The mutation rate of organisms like viruses and bacteria is defined as the probability that a change in genetic information is passed to the next generation. For viruses, this is often measured through the infection cycle of a cell. Unlike in insects, resistance in viruses and bacteria can be driven by mutational events during reproduction.

Viral resistance to vaccines can be due to high mutation rates allowing for rapid changes in viral proteins that interact with the immune system. Similarly, bacterial resistance to antibiotics and other medications can arise through the evolution of new genetic pathways that help them survive the presence of these drugs. For insects, the adaptation to pesticides is driven by the survival and reproduction of insects carrying resistance genes.

For viruses, the mutation rate and the mechanism of resistance are highly dependent on the specific genetic makeup and the selective pressures imposed by the environment. Understanding these mechanisms is crucial for developing effective vaccines and medications that can combat these adaptable organisms.

Keywords: epigenetics, gene expression, environmental impact

To learn more about Duke's research on epigenetics and to explore the intersection of genetics and the environment, visit Duke genetic studies.