Practice Tests
IELTS Reading (AC) Task 1 #157

A. Epigenetics is a rapidly advancing field of biology that studies how behaviours and environment can cause changes that affect the way our genes work. Unlike genetic changes, which involve alterations to the DNA sequence itself, epigenetic changes are modifications that are "on top of" or "in addition to" the traditional genetic basis for inheritance. These changes can switch genes on or off without changing the underlying DNA code, and they play a crucial role in cell differentiation, development, and disease.

B. The two most well-understood epigenetic mechanisms are DNA methylation and histone modification. DNA methylation involves adding a chemical group to parts of the DNA molecule, which can prevent certain genes from being expressed. Histone modification refers to changes to the proteins, called histones, around which DNA is wrapped. These modifications can alter how tightly the DNA is packaged, making genes more or less accessible to be read and transcribed.

C. Epigenetic changes are a natural part of life. They are what allow a single fertilised egg to develop into the many different cell types, such as skin cells, liver cells, and brain cells, that make up a complex organism. All these cells have the same DNA, but their epigenetic marks determine which genes are active, giving each cell its specialised function. However, the epigenome is also dynamic and can be influenced by a wide range of external factors throughout a person''s life, including diet, stress, exercise, and exposure to toxins.

D. The study of epigenetics is transforming our understanding of health and disease. It helps to explain how environmental factors can influence disease risk and how some diseases, like certain cancers, can develop without any apparent genetic mutation. Because epigenetic changes are potentially reversible, this field offers exciting new possibilities for therapies that could target and reverse the epigenetic modifications associated with various diseases, opening up a new frontier in personalised medicine.