DNA Structure and Function

DNA Structure

• DNA consists of two strands that form a spiraling ladder, known as a double helix
• Each strand is composed of sugar and phosphate molecules, forming the backbone
• The center rungs of the DNA ladder are composed of four types of nitrogenous bases:
  • Adenine (A)
  • Thymine (T)
  • Guanine (G)
  • Cytosine (C)
• Complementary base pairing occurs between:
  • Adenine (A) and Thymine (T)
  • Guanine (G) and Cytosine (C)
• Adenine and Guanine have double-ringed structures, while Thymine and Cytosine have single-ringed structures

Role of DNA in Evolution

• DNA is the genetic blueprint of life found within chromosomes in every living cell
• DNA determines genes, which in turn determine traits
• Mutations in DNA can lead to variations in a species, with favorable mutations being passed on to offspring
• Genetic variation is essential for evolution

Types of Evolution

• Microevolution:
  • Minor changes in a species due to adaptations to changing environments
  • Results from genetic variation acted on by natural selection
  • Changes may include differences in color, size, or behavior
  • These changes may or may not lead to the creation of a new species
• Macroevolution:
  • Evolution above the species level, examining common descent
  • Utilizes comparative anatomy, embryology, biochemistry, and paleontology
  • Involves extensive inference, creating some uncertainty

Summary

• Evolution: Gradual change in the genetic composition of a population over successive generations
• Microevolution: Short-term adaptations within a species
• Macroevolution: Large-scale evolutionary changes leading to new species

This quiz covers the basic structure of DNA, including the double helix model, nitrogenous bases, and complementary base pairing. Understand the composition of DNA strands and the characteristics of each base.