DNA and RNA Structure DNA and RNA are nucleic acids, polymers made of subunits called nucleotides. This is a close-up of one DNA nucleotide. A DNA nucleotide is composed of a nitrogenous base, phosphate group, and a deoxyribose sugar. One difference between DNA and RNA is the type of sugar their nucleotides contain. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. Ribose has one more oxygen atom than deoxyribose. DNA and RNA are each composed of four different nucleotides, which differ in their nitrogenous bases. Three of the four bases are the same in DNA and RNA- adenine, guanine, and cytosine. The fourth base in DNA is thymine. In RNA it is uracil. The nitrogenous bases guanine and adenine each have two linked rings of atoms. They are called purines. Cytosine, thymine, and uracil each have a single ring, and these three bases are called pyrimidines. For convenience, the carbon atoms in a nucleotide's sugars are numbered beginning with the carbon atom bonded to the nitrogenous base, moving around the ring, and up to the carbon that is bonded to the phosphate group. The 1 prime carbon is bonded to the nitrogenous base, the 3 prime carbon to the next nucleotide, and the 5 prime carbon to the phosphate group. DNA and RNA are polynucleotides - long chains of nucleotides. Polynucleotides are always assembled in the 5 prime to 3 prime directions. A covalent bond forms between the carbon at the 3 prime position of a nucleotide and the phosphate group at the 5 prime position of the next nucleotide. RNA usually consists of a single polynucleotide chain. DNA, on the other hand, consists of two polynucleotide chains. The two DNA chains, or strands, are oriented in opposite directions and held together by hydrogen bonds between the nitrogenous bases on opposite strands. Because of their sizes, shapes, and arrangement of polar groups, the DNA bases form complementary pairs. Adenine pairs with thymine, and cytosine pairs with guanine. The two polynucleotides in DNA wind around each other to form the familiar double helix. The bases can be in any order, like the letters of the alphabet. However, the base sequence is significant. Sequences of bases called genes encode the instructions for the structure and function of an organism.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
4. Biomolecules
Nucleic Acids
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