DNA

• Organic


  Chemical compounds that contain carbon, are complex, and are produced by or associated with living things
• Inorganic


  Chemical compounds that do not meet the criteria for organic compounds
• Main organic compounds found in organisms

  • Nucleic Acids (DNA and RNA)
  • Proteins
  • Carbohydrates
  • Lipids
• Macromolecules


  Large and complex biological molecules made up of smaller subunits (monomers)
• Subunits of biological molecules

  • Saccharides (for carbohydrates)
  • Amino acids (for proteins)
  • Fatty acids (for lipids)
  • Nucleotides (for DNA)
• Amino acids


  Linked together to form proteins, each has a unique 'R' group
• There are 20 different amino acids commonly found in proteins
• Nucleic acids


  Polymers made up of the subunits nucleotides
• Nucleotides


  Comprised of a phosphate group, a sugar, and a nitrogen base
• DNA


  A molecule which stores the information to direct complex cellular processes and can self-replicate
• RNA


  A type of nucleic acid required in protein synthesis
• DNA


  • It is a very long polymer with a double helix structure
  • The genetic code is the same for all living things
• DNA replication


  DNA can self-replicate, allowing it to be copied prior to cell division and passed on to daughter cells
• Deoxyribonucleic Acid (DNA)


  The building blocks are nucleotides, which have a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogen base
• One strand of DNA is a polymer of millions of nucleotides
• The four nitrogen bases in DNA

  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T)
• Complementary base pairing


  A always pairs with T, and G always pairs with C due to the ability to form hydrogen bonds
• The two strands of DNA are arranged in opposite directions (anti-parallel)
• The haploid human genome contains approximately 3 billion base pairs of DNA packaged into 23 chromosomes
• Most cells in the human body are diploid, with 23 pairs of chromosomes, containing a total of 6 billion base pairs of DNA
• The total length of DNA in the human body is estimated to be enough to go from the Earth to the Sun and back over 300 times
• During DNA replication, only about one error occurs for every one billion nucleotides made
• Telomeres


  The caps at the end of each strand of DNA that protect our chromosomes
• Telomeres get shorter each time a cell copies itself, eventually becoming too short to do their job, causing cells to age and stop functioning properly
• Telomeres can be shortened by stress, smoking, obesity, lack of exercise, and a poor diet
• Differences between DNA and RNA

  • DNA is double-stranded, RNA is single-stranded
  • DNA uses deoxyribose sugar, RNA uses ribose sugar
  • DNA uses thymine, RNA uses uracil
• Differences between prokaryotic and eukaryotic chromosomes

  • Prokaryotic chromosomes are circular, eukaryotic chromosomes are linear
  • Prokaryotic chromosomes have no histone proteins, eukaryotic chromosomes have histone proteins
  • Prokaryotes have one chromosome, eukaryotes have multiple chromosomes
  • Prokaryotic chromosomes have no introns, eukaryotic chromosomes have introns
• Chromatid


  Either of the two strands of a replicated chromosome
• Chromatin


  A mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division
• Chromosome


  Single-stranded groupings of condensed chromatin
• Chromosomes replicate to ensure each new daughter cell receives the correct number of chromosomes during cell division
• Centromere


  The central region where sister chromatids are connected
• Humans have 46 chromosomes
• Homologous chromosomes


  Chromosomes containing the same type of genetic information, one from the male parent and one from the female parent
• Gene


  Segment of DNA that has the information (the code) for a protein or RNA
• Human beings have 20,000 to 25,000 genes, which account for only about 3 per cent of our DNA
• Introns


  Non-coding regions of a gene
• Exons


  Coding regions of a gene
• Only eukaryotes contain introns in the coding region
• In eukaryotes, both introns and exons are transcribed into the primary transcript