Dna double helix

Definition

The DNA double helix is the molecular structure of deoxyribonucleic acid (DNA), consisting of two long strands of nucleotides twisted around each other, forming a helical shape. This structure is essential for the storage and transmission of genetic information, as it allows DNA to replicate accurately and provides stability against environmental factors that could damage the genetic code.

5 Must Know Facts For Your Next Test

1. The double helix structure was first described by James Watson and Francis Crick in 1953, based on X-ray diffraction data provided by Rosalind Franklin.
2. Each strand of the DNA double helix is made up of alternating sugar and phosphate groups, forming the backbone, while the nitrogenous bases protrude inward.
3. The two strands of the double helix are antiparallel, meaning they run in opposite directions, which is crucial for replication and enzyme function.
4. The stability of the double helix is largely due to the hydrogen bonds formed between the base pairs, as well as the stacking interactions between adjacent base pairs.
5. DNA can undergo supercoiling in cells, allowing it to pack efficiently into chromosomes while maintaining its structural integrity for replication and transcription.

Review Questions

• How does the structure of the DNA double helix facilitate its function in genetic information storage and transmission?
  • The DNA double helix structure facilitates its function by providing a stable yet flexible framework for storing genetic information. The specific base pairing between adenine-thymine and guanine-cytosine allows for accurate replication during cell division. The helical shape also protects the genetic code from environmental damage while allowing access to necessary enzymes for processes such as transcription and replication.
• Discuss the importance of base pairing in maintaining the integrity of the DNA double helix during replication.
  • Base pairing is crucial for maintaining the integrity of the DNA double helix during replication because it ensures that each new strand is an exact complement of its template strand. The specific pairing of adenine with thymine and guanine with cytosine minimizes errors during copying. This specificity allows DNA polymerases to accurately synthesize new strands, resulting in two identical double helices from one original DNA molecule.
• Evaluate the impact of X-ray diffraction techniques on our understanding of the DNA double helix structure and its biological significance.
  • X-ray diffraction techniques were pivotal in elucidating the structure of the DNA double helix, as they provided critical evidence for its helical shape and dimensions. The work of Rosalind Franklin in capturing high-resolution images allowed Watson and Crick to propose their model accurately. This breakthrough not only transformed molecular biology by providing insights into how genetic information is stored but also laid the foundation for advances in genetics, biotechnology, and medicine by highlighting how alterations in this structure can lead to mutations and diseases.

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 hydrogen bonding between nitrogenous bases in DNA, where adenine pairs with thymine and guanine pairs with cytosine.

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