Double helix

Definition

The double helix is the structural arrangement of DNA, consisting of two strands that coil around each other, resembling a twisted ladder. This configuration is crucial for the stability and replication of genetic material, with each strand composed of nucleotides that include a sugar, a phosphate group, and a nitrogenous base. The double helix structure allows for the complementary pairing of bases, which is fundamental in the process of DNA replication and protein synthesis.

5 Must Know Facts For Your Next Test

1. The double helix structure was first described by James Watson and Francis Crick in 1953, which was a pivotal moment in genetics.
2. The two strands of the double helix are held together by hydrogen bonds between the complementary nitrogenous bases.
3. The double helix structure is essential for the accurate replication of DNA, as each strand serves as a template for creating a new complementary strand.
4. The orientation of the strands in the double helix is antiparallel, meaning one strand runs in the opposite direction to the other.
5. Mutations in the DNA sequence can disrupt the double helix structure, potentially leading to genetic disorders or diseases.

Review Questions

• How does the structure of the double helix contribute to the stability and function of DNA?
  • The double helix structure contributes to the stability of DNA by allowing base pairs to form hydrogen bonds between the strands, which helps maintain its integrity. The coiling nature of the double helix also protects the genetic information stored within from damage. Additionally, this structure facilitates DNA replication by providing complementary templates for new strands to form, ensuring that genetic information is accurately passed on during cell division.
• In what ways does base pairing support the processes of DNA replication and protein synthesis?
  • Base pairing is critical during DNA replication because it ensures that each new strand formed is complementary to its template strand, thus preserving genetic fidelity. During protein synthesis, base pairing occurs when mRNA is transcribed from DNA and later translated into proteins. The specific pairing rules (adenine with thymine and cytosine with guanine) ensure that the genetic code is accurately converted into functional proteins, which are essential for various cellular functions.
• Evaluate the implications of mutations in the context of the double helix structure and how they can affect an organism's phenotype.
  • Mutations in the DNA sequence can lead to alterations in the double helix structure, affecting how genes are expressed or how proteins are produced. These changes can result from errors during DNA replication or external factors like radiation or chemicals. Depending on where they occur and their nature, mutations can have various effects on an organism's phenotype, ranging from harmless variations to serious genetic disorders or even cancer. Understanding these implications highlights the importance of maintaining DNA integrity for overall health and development.

Related terms

Nucleotide: The basic building block of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.

Base Pairing: The specific pairing of nitrogenous bases in DNA, where adenine pairs with thymine and cytosine pairs with guanine.

DNA Replication: The process by which DNA makes a copy of itself during cell division, ensuring that each daughter cell receives an identical set of genetic information.