Question

Which would you expect to have a higher entropy: DNA in its well-known double- helical form, or DNA with the strands separated?

Short answer

Separated strands of DNA have higher entropy than double-helical DNA.

Step-by-step solution

Understand the Concept of Entropy

Entropy is a measure of the disorder or randomness in a system. A system with higher entropy is more disordered and has more possible microstates.

Analyze Double-Helical DNA

In its double-helical form, DNA is structured and ordered. The two strands are coiled around each other, forming a stable configuration with fewer possible microstates.

Analyze Separated DNA Strands

When the DNA strands are separated, each strand is free to move independently. This increases the number of possible configurations and thus the number of microstates, leading to higher entropy.

Compare the Entropy

Comparing the structured, double-helical form and the unstructured, separated strands of DNA, the separated strands have higher entropy due to their increased disorder and number of possible microstates.

Conclusion

Based on the comparison, one would expect the separated DNA strands to have higher entropy than the double-helical DNA.

Key concepts

Entropy

Entropy is a key concept in thermodynamics, and it describes the level of disorder or randomness in a system. Essentially, a system with higher entropy is more disordered and less predictable. In mathematical terms, entropy indicates the number of possible ways a system's energy can be arranged. When thinking about entropy in biological systems like DNA, it's useful to remember that higher entropy means a state with more possible configurations. This results in more microstates for the system.

Microstates

Microstates refer to the specific arrangements of particles or energy within a system. Each microstate is a unique configuration that the system can adopt. The more microstates a system has, the higher its entropy. For example, DNA separated into two strands has many more possible microstates compared to its double-helical form. The flexibility and freedom of the separated strands allow for a greater number of potential configurations, leading to increased entropy.

DNA Structure

DNA is a molecule that carries genetic information in all living organisms. Its structure is key to its function. DNA is composed of two strands that form a double helix. This double-stranded structure is very stable and ordered. Each strand consists of repeating units called nucleotides, which pair specifically—adenine with thymine, and cytosine with guanine. This specific pairing and coiled structure result in fewer possible configurations, meaning lower entropy compared to other states of the DNA molecule.

Double Helix

The double helix is the well-known shape of DNA when its two strands are coiled around each other. This structure is stabilized by hydrogen bonds between paired nucleotides. Because the double helix is highly ordered, it has fewer possible ways to arrange its molecules, leading to lower entropy. The double helix's organized structure is crucial for the accurate replication and functioning of DNA within cells. However, when the strands are separated, they lose this order and can adopt many different configurations.

Disorder

Disorder in scientific terms often refers to the lack of predictability and order within a system. In the context of DNA, disorder refers to the increase in possible configurations and microstates when the DNA strands are separated. The separated strands can move and flex independently, resulting in higher entropy. This higher entropy state signifies a more disordered system, compared to the highly ordered and stable double helix form. Thus, understanding disorder helps explain why separated DNA strands have higher entropy.