Epistasis
Epistasis is a genetic phenomenon where the effect of one gene is dependent on the presence of one or more ‘modifier genes.’ In simpler terms, it means that one gene can mask or alter the expression of another gene. This interaction can significantly influence traits in an organism. For example, consider the coat color in mice. If one gene determines the coat color (say, black or brown), another gene (the epistatic gene) might mask this color entirely, resulting in a completely different color, such as white. Epistasis highlights the complexity of genetic interactions and how they can lead to a variety of phenotypes.
Epigenetics
Epigenetics refers to the study of changes in gene expression or cellular phenotype that do not involve alterations to the underlying DNA sequence. These changes can be influenced by several factors including age, environment, and lifestyle. One of the most common mechanisms of epigenetic change is DNA methylation, where methyl groups are added to the DNA molecule, affecting how genes are turned on or off. This means that even if two individuals have the same DNA sequence, environmental factors can lead to different traits being expressed. This field has opened up new understandings of heredity, where traits acquired during one’s lifetime can potentially be passed down to future generations without changes to the actual DNA sequence.