NUCLEIC ACIDS

• Heredity - is the transfer of characteristics from a parent organism from generation to generation
• Chromosomes – the anatomical structure found in the nucleus which contains
• Genes – biochemical carriers of the traits
• Genome – a collection of genes of an individual
• Genes contain instructions for making proteins
• Proteins act alone or in complexes to perform many cellular functions
• 1967 - Gregor Mendel noted inheritance of traits in peas. He cultivated and studied thousands of pea plants in his garden.
• 1969 - Friedrich Miescher discovered a substance containing P and N2 in the nuclei of white blood cells found in pus. He discovered DNA.
• 1903 - WS Sutton proposed the “Chromosome Theory”
• 1928 - Frederick Griffith noted transformation in bacteria
• 1944 - Oswald Avery, Collin Mcleod and Maclyn McCarthy used degrading enzymes to determine the genetic material
• 1952 - Hershey and Chase discovered that genetic material of bacteriophage are transferred to bacteria
• Nucleic Acid - polymer of nucleotides
• DNA - Deoxyribonucleic Acid
• RNA - Ribonucleic Acid
• There are two kinds of nucleic acids in cells:

  • ribonucleic acids (RNA)
  • deoxyribonucleic acids (DNA)
• Both RNA and DNA are polymers built from monomers called nucleotides.
• A nucleotide is composed of:

  • a base, a monosaccharide, and a phosphate.
• Nucleotide: a nucleoside in which a molecule of phosphoric acid is esterified with an -OH of the monosaccharide, most commonly either the 3’ or the 5’-OH.
• Nucleoside: a compound that consists of D-ribose or 2-deoxy-D-ribose bonded to a purine or pyrimidine base by a β-N-glycosidic bond.
• Bases of Nucleic Acids

  • Purine Bases
  • Pyrimidine Bases
• Purine Bases

  • AdeninE
  • Guanine
• Pyrimidine Bases

  • Cytosine
  • Thymine
  • Uracil
• Phosphodiester bonds link nucleotides to form nucleic acids
• 1953

  • Rosalind Franklin and Maurice Wilkens had “x-ray pictures” of DNA
• Rosalind Franklin – through X-ray diffraction Dr. Rosalind Franklin discover the structure of DNA. She demonstrated the double-helix structure of DNA (the molecule containing the genetic instructions for the progress or development of all living organisms.
• Maurice Wilkin – he played an important role in the discovery of the double helix structure of DNA. Wilkin and his student Ray Gosling used X-ray diffraction to take new images of a form of DNA molecule.
• The DNA double helix (1953)

  • Presented by James Watson and Francis Crick
  • Most significant discovery in biology in the 20th century
  • Article presented in Nature
• In 1953 James Watson and Francis Crick proposed a structure for DNA that not only accounts for the pairing of bases but also accounts for the storage and transfer of genetic information.
• Nobel Prize Award in 1962 for the discovery of DNA Structure
• Erwin Chargaff “Chargaff rules”
• DNA was not a single stranded molecule but rather a duplex
• Molecule was helical in nature
• The two strands were held together by hydrogen bonds
• The two strands of DNA were antiparallel
• Nitrogen bases paired in complementary fashion (A&T and C&G to account for Chargaff's data)
• Duplex - Composed of 2 separate molecules that form a complex
• Hydrogen bonds between complementary bases stabilizes the double stranded DNA molecule
• Hydrogen bonding between bases

  • G pairs with C with triple hydrogen bonds
  • A pairs with T with double hydrogen bonds
• Primary Structure of the DNA

  • Sequential arrangement of nucleotide bases
  • Has a 5’ to 3’ notation (According to Watson & Crick Model, A always bonds to T, and C always bonds to G)