Molecular Genetics

• DNA replication occurs through semiconservative replication, where the two strands separate and serve as templates for new nucleotides to be added.
• The DNA double helix is held together by hydrogen bonds between complementary base pairs.
• The DNA polymerase enzyme adds complementary bases to the template strand, forming a new double-stranded molecule that is identical to one of the original parental strands.
• Helicase enzymes break the hydrogen bonds holding the bases together, separating the two strands into single-stranded DNA molecules.
• Nucleotides contain a phosphate group, a deoxyrobose, and a nitrogenous base
• Rosalind Franklin took photo 51 in 1952. It was a 100 hour process. Her work was stolen by Watson and Crick who won a nobel prize for their work. She died of cancer due to her exposure to x-ray radiation.
• Erwin Chargaff discovered that the ratio of the number of A's to T's and of C's to G's in DNA is 1:1. (He discovered "base-pairs"). He did this using paper chromatography.
• James Watson and Francis Crick proposed the structure of DNA as a double helix with antiparallel strands joined by hydrogen bonding between complementary base pairs.
• DNA replication occurs through semiconservative replication where each daughter molecule contains one old and one newly synthesized strand.
• Label diagram of DNA structure.

  A) cytosine

  B) thymine

  C) adenine

  D) uracil

  E) hydrogen bonds

  F) nitrogenous bases

  G) guanine

  H) sugar phosphate backbone

  I) base pairs

  J) nucleotide

  
• What is a purine?

  A nitrogenous base with a double ring such as adenine and guanine.
• what is a pyrimidine?


  A nitrogenous base with a single ring such as cytosine, thymine and uracil.
• What type of covalent bond connects the nucleotides together?

  A phosphodiester bond holds the deoxyribose to the phosphate group along the backbone.
• DNA replication takes place during interphase.
• Replication is semiconservative.
• Label the replication fork

  A) single stand binding protein

  B) leading strand

  C) DNA polymerase 3

  D) primase

  E) helicase

  F) lagging strand

  G) DNA polymerase 1

  H) original DNA strand

  I) primer

  J) ligase

  K) 5'

  L) 3'

  
• gyrase is a type of topoisomerase which makes little cuts in the original DNA strand to reduce tension.
• Okazaki fragments are the fragments of new DNA made on the lagging strand due to discontinuous synthesis.
• The tRNA activation enzyme catabolizes the bond between the amino acid and the tRNA releasing it to the peptide chain.
• label the lac operon

  A) regulatory gene

  B) promoter

  C) operator

  D) repressor protein

  E) lac operon

  F) inducer