Monozygotic Twins

Question

Monozygotic twins are said to be identical, meaning both their genomes are exactly the same at birth. Over time however, their phenotypes can change as they age. What are two mechanisms that allow this to happen?

Answer 1

One mechanism is epigenetic changes such as alterations in chromosome structure. This can increase or decrease gene expression depending on the modification. Another mechanism is random mutations that accumulate over time when the DNA is replicated.