Central Dogma

1. Central Dogma • Central Dogma: DNA codes for RNA which guides the synthesis of proteins. • DNA: “master blueprint”, contains all genetic info of an organism. Must be protected; therefore it never leaves the nucleus. • RNA: “temporary blueprint”, copies small portions of DNA and can leave nucleus to synthesize proteins at the ribosome. • Proteins: primary building block of organisms. A macromolecule made of linked monomers called amino acids. DNA RNA Protein Transcription “copy” Translation “interpret”

2. Central Dogma • Transcription: DNA  mRNA “messenger” • DNA helicase (enzyme) unwinds DNA strands. • RNA polymerase (enzyme) “reads” DNA template strand & synthesizes mRNA • Matches nitrogen bases on DNA to complementary RNA bases • 3. mRNA leaves nucleus through nuclear pore to the cytoplasm DNARNA A = U T = A C  G G  C

3. Translation: mRNA  Protein codon • mRNA travels through cytoplasm to ribosome (made of rRNA) • tRNAs bring amino acids to the ribosome • The ribosome matches tRNA anticodons to mRNA codons, which links amino acids together, creating a polypeptide (unfolded protein) • **Note: 20 different tRNA (one for each amino acid)

4. Central Dogma • How do you know what amino acid is brought by tRNA? Genetic Code Chart(uses codons from mRNA!) • AUG: methionine (START) • Begin decoding; start with methanine amino acid • UAA, UAG, UGA: STOP • End decoding; no additional amino acids **Note: Many types of codons (64 codons), but only 20 amino acids. Important when we learn about mutations! Image Source: waynesword.palomar.edu

5. Image Source: www.contexo.info Central Dogma • Example: Folded into complex 3D shape  Protein!