Living Environment Regents Practice Test

What is a characteristic of identical twins in terms of genetic markers?

1. They will always have the same epigenetic markers.

2. They can have different markers attached to their genes from birth.

3. They share all environmental factors completely.

4. They have no genetic similarity.

The correct answer is: They can have different markers attached to their genes from birth.

Identical twins, also known as monozygotic twins, originate from a single fertilized egg that splits into two embryos, making them genetically identical with the same DNA sequence. However, despite this genetic similarity, they can exhibit differences in their epigenetic markers. Epigenetic markers are chemical modifications that influence how genes are expressed without altering the DNA sequence itself. These markers can be affected by various factors including environmental influences, nutrition, and individual experiences, leading to variations in gene expression over time. The assertion that identical twins can have different markers attached to their genes from birth is correct because while they start with the same genetic blueprint, their environments and experiences can lead to the accumulation of different epigenetic changes as they grow, resulting in variations in traits or health. This highlights the dynamic interaction between genetics and environment in the development of identical twins. Factors such as lifestyle choices, exposure to toxins, diet, stress, and even social interactions can contribute to these differences in epigenetic markers. Thus, while identical twins share the same genetic makeup, their experiences can create divergences at the epigenetic level.