Central Dogma of Life

• Chromosomes - Strands of DNA that contain all of the genes an organism needs to survive and reproduce
• Genes - Segments of DNA that specify how to build a protein
• Chromosome maps are used to show the locus (location) of genes on a chromosome
• Different genes (genomes) --- different proteins (proteomes)
• Different versions of the same gene (alleles)
•  A region of the chromosome remains uncopied (centromere) in order to hold the sister chromatids together
• • Recall that Adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C)
• The process is semiconservative because each new double-stranded DNA contains one old strand (template) and one newly-synthesized complementary strand
• DNA Polymerase - Enzyme that catalyzes the covalent bond between the phosphate of one nucleotide and the deoxyribose (sugar) of the next nucleotide
• 3’ end has a free deoxyribose

  5’ end has a free phosphate
• Primase (a type of RNA polymerase) builds an RNA primer (5-10 ribonucleotides long)
• • DNA polymerase attaches onto the 3’ end of the RNA primer
• Elongation

  • DNA polymerase uses each strand as a template in the 3’ to 5’ direction to build a complementary strand in the 5’ to 3’ direction
• Topoisomerase - unwinds DNA
• Helicase – enzyme that breaks H-bonds
• DNA Polymerase – enzyme that catalyzes connection of nucleotides to form complementary DNA strand in 5’ to 3’ direction (reads template in 3’ to 5’ direction)
• Leading Strand – transcribed continuously in 5’ to 3’ direction
• Lagging Strand – transcribed in segments in 3’ to 5’ direction (Okazaki fragments)
• DNA Primase – enzyme that catalyzes formation of RNA starting segment (RNA primer)
• DNA Ligase – enzyme that catalyzes connection of two Okazaki fragments