Question

List the postulates of the Watson-Crick model of DNA secondary structure.

Short answer

Answer: The main postulates of the Watson-Crick model of DNA secondary structure include the double helix structure, complementary base pairing, antiparallel strands, and semiconservative replication. This model has significantly contributed to our understanding of genetics and molecular biology.

Step-by-step solution

1. Introduction to the Watson-Crick model

The Watson-Crick model, proposed by James Watson and Francis Crick in 1953, describes the structure and properties of the DNA molecule. This model, also known as the double helix model, was a groundbreaking discovery that provided valuable insights into genetics and molecular biology.

2. Double helix structure

The first postulate of the Watson-Crick model is that DNA consists of two polynucleotide strands that coil around each other to form a double helix. Each strand is composed of a sugar-phosphate backbone and nucleotide bases.

3. Complementary base pairing

The second postulate focuses on the pairing of nucleotide bases. In the Watson-Crick model, the bases pair in a specific and complementary way: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). This base pairing is called complementary base pairing.

4. Antiparallel strands

The third postulate states that the two strands of DNA are antiparallel in orientation. This means that the 5' end (the end with the phosphate group) of one strand is paired with the 3' end (the end with the sugar group) of the other strand, and vice versa. This antiparallel orientation is crucial for DNA replication and synthesis.

5. Semiconservative replication

The fourth postulate of the Watson-Crick model proposes that DNA replication is semiconservative. When a DNA molecule replicates, each of the two daughter molecules contains one original parent strand and one newly synthesized strand. This ensures that the genetic information is accurately passed on to the next generation. In summary, the main postulates of the Watson-Crick model of DNA secondary structure are the double helix structure, complementary base pairing, antiparallel strands, and semiconservative replication. This model has been pivotal in our understanding of genetics and the molecular mechanisms of life.