DNA Structure and Components

DNA Structure

Double Helix Model

• DNA is composed of two complementary strands that twist together to form a double helix
• The strands are held together by hydrogen bonds between nitrogenous bases

Nitrogenous Bases

• There are four nitrogenous bases found in DNA:
  1. Adenine (A)
  2. Guanine (G)
  3. Cytosine (C)
  4. Thymine (T)
• Base pairing rules:
  • Adenine (A) pairs with Thymine (T)
  • Guanine (G) pairs with Cytosine (C)

Sugar-Phosphate Backbone

• The sugar-phosphate backbone is composed of:
  • Deoxyribose sugar molecules
  • Phosphate groups
• The sugar and phosphate molecules make up the outer backbone of the DNA double helix

DNA Dimensions

• The diameter of the DNA double helix is approximately 2 nanometers
• The distance between each base pair is approximately 0.34 nanometers
• The length of a DNA molecule can vary greatly, ranging from a few thousand to millions of base pairs

Right-Handed vs. Left-Handed DNA

• The double helix structure of DNA can be either right-handed or left-handed
• Right-handed DNA is the most common form found in nature
• Left-handed DNA is less common and is often found in certain viral genomes

DNA Structure

Double Helix Model

• Composed of two complementary strands twisted together to form a double helix
• Strands held together by hydrogen bonds between nitrogenous bases

Nitrogenous Bases

• Four nitrogenous bases found in DNA: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T)
• Adenine (A) pairs with Thymine (T)
• Guanine (G) pairs with Cytosine (C)

Sugar-Phosphate Backbone

• Composed of deoxyribose sugar molecules and phosphate groups
• Sugar and phosphate molecules make up the outer backbone of the DNA double helix

DNA Dimensions

• Diameter of DNA double helix is approximately 2 nanometers
• Distance between each base pair is approximately 0.34 nanometers
• Length of a DNA molecule can vary greatly, ranging from a few thousand to millions of base pairs

Right-Handed vs. Left-Handed DNA

• Double helix structure of DNA can be either right-handed or left-handed
• Right-handed DNA is the most common form found in nature
• Left-handed DNA is less common and is often found in certain viral genomes