In this chapter, we focused on a mode of inheritance referred to as quantitative genetics, as well as many of the statistical parameters utilized to study quantitative traits. Along the way, we found opportunities to consider the methods and reasoning by which geneticists acquired much of their understanding of quantitative genetics. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:

How do we know that monozygotic twins are not identical genotypically as adults?

Key Concepts

Monozygotic Twins

Monozygotic twins, also known as identical twins, originate from a single fertilized egg that splits into two embryos. While they share the same genetic material at conception, environmental factors and epigenetic changes can lead to differences in gene expression as they develop. This means that, despite their identical DNA, they may not be phenotypically or genotypically identical as adults.

Epigenetics

Epigenetics refers to the study of changes in gene expression that do not involve alterations to the underlying DNA sequence. Factors such as environmental influences, lifestyle, and experiences can lead to epigenetic modifications, which can affect how genes are turned on or off. These changes can result in differences between monozygotic twins, highlighting that genetics is not the sole determinant of phenotype.

Quantitative Traits

Quantitative traits are characteristics that are influenced by multiple genes and environmental factors, leading to a continuous range of phenotypes. Examples include height, weight, and skin color. The study of quantitative genetics involves statistical methods to analyze the inheritance patterns of these traits, helping to understand how genetic and environmental factors contribute to phenotypic variation, including differences observed in monozygotic twins.