Question

When samples of double-stranded DNA are analyzed, the quantity of adenine present equals that of thymine. Similarly, the quantity of guanine equals that of cytosine. Explain the significance of these observations.

Short answer

The significance of the observation that adenine (A) equals thymine (T) and guanine (G) equals cytosine (C) in double-stranded DNA lies in the base pairing rules which state that A pairs with T and G pairs with C. These rules ensure that the DNA molecule's two strands are complementary to each other, maintaining the stability of the DNA molecule, properly transmitting genetic information during replication, and minimizing errors that could lead to mutations. This observation is crucial for preserving the integrity of genetic information stored in DNA.

Step-by-step solution

Understanding the structure of DNA

Double-stranded DNA is a complex molecule that contains genetic information for the synthesis of proteins and other molecules needed for cellular processes. Its structure consists of two complementary strands that run in opposite directions and are held together by hydrogen bonds between nitrogenous bases. The sequence of these bases encodes the genetic information in the DNA molecule.

The nitrogenous bases in DNA

DNA contains four types of nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C). These bases play an essential role in storing genetic information and transmitting it during replication.

Base pairing rules and complementary strands

The significance of the observation lies in the base pairing rules, which state that adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). This is due to the specific hydrogen bonds that form between these bases, ensuring that the two strands of the DNA molecule are complementary to each other. In other words, every time there is an adenine (A) on one strand, there will be a thymine (T) on the opposite strand, and every time there is a guanine (G) on one strand, there will be a cytosine (C) on the opposite strand. Therefore, the quantity of adenine (A) will always equal the quantity of thymine (T), and the quantity of guanine (G) will always equal the quantity of cytosine (C).

Importance of base pairing rules

The base pairing rules are crucial for maintaining the integrity of the genetic information stored in DNA, as they ensure that the two strands of the DNA molecule can come together to form a stable structure and can be accurately replicated during cell division. When DNA replicates, the two strands of the double helix separate, and each strand serves as a template for the synthesis of a new complementary strand. If the base pairing rules were not conserved, errors could occur during replication, leading to mutations in the genetic information that could have negative consequences for the organism. In summary, the observation that adenine (A) equals thymine (T) and guanine (G) equals cytosine (C) in double-stranded DNA is a direct consequence of the base pairing rules that maintain the stability and proper functioning of the DNA molecule.