Molecular Biology of the Gene PART 2

1. Molecular Biology of the GenePART 2 Debbi Ann Morrissette Graduate Student Researcher Laboratory of Molecular Neuropathogenesis University of California, Irvine

2. PART 1 • Structure of DNA • DNA Replication • DNA vs. RNA PART 2 • Flow of Genetic Info • Mutations • Cloning • Differentiation • X Chromosome Inactivation

3. The 2 Main Functions of DNA • Passing genetic information to daughter cells • Through DNA replication DNA • Directing the synthesis of proteins • Through transcription of the DNA code and translation of the nucleotide code into an amino acid sequence RNA

4. Nitrogenous Base Phosphate Sugar Basic Nucleotide Stucture

5. Nitrogenous Bases U C A G DNA vs. RNA Deoxyribonucleic Acid Ribonucleic Acid H Uracil Thymine CH3 Nitrogenous Base Nitrogenous Base Phosphate Phosphate Sugar Sugar Ribose Deoxyribose H OH Nitrogenous Bases T C A G

6. A T C C A A T T C G A T C G C T G U T A G A A C U C A C T A C • DNA:RNA (transcription) • A:U • C:G • T:A A G A T T G G T A Base Pairing • DNA:DNA (replication) • A:T • C:G

7. DNA Transcription RNA Translation Protein From DNA to Proteins Genotype Phenotype

8. DNA molecule Gene 1 Gene 2 Gene 3 DNA strand C C G G C A A A A A A A Transcription C G G U U U U U C G U U RNA Codon Translation Polypeptide Amino acid Note: U pairs with A A still pairs with T Overview Genotype Phenotype

9. A A A G U U U U G G The RNA “Players” • mRNA = messenger RNA • “The Mailman” • rRNA = ribosomal RNA • “The Recruiter” • tRNA = transfer RNA • “The Translator”

10. RNA polymerase DNA of gene Promoter DNA Terminator DNA Initiation Initiation Elongation Growing RNA Termination Completed RNA RNA polymerase Transcription • Initiation • RNA polymerase attaches to the promoter sequence on DNA strand • Elongation • RNA polymerase moves along the DNA strand adding complementary RNA nucleotides to make the mRNA strand • Termination • RNA reaches the terminator sequence on the DNA strand and releases from the DNA

11. RNA nucleotides RNA polymerase C C A A T T A U T C T G U G A C A C U C A C C A G A T T G T G A Direction of transcription Template strand of DNA Newly made RNA Elongation –A Closer Look

12. _______________ _______________ _______________ mRNA • Following transcription, the “message” is brought from the nucleus to the cytoplasm.

13. A A A G U U U U G G The RNA “Players” • mRNA = messenger RNA • “The Mailman” • rRNA = ribosomal RNA • “The Recruiter” • tRNA = transfer RNA • “The Translator”

14. Met A A A G U U U U G G Large ribosomal subunit U C A G U A Small ribosomal subunit mRNA tRNA rRNA Translation • rRNA recruits both mRNA and tRNA

15. Amino acid attachment site Anticodon tRNA • tRNA must translate the RNA message carried by mRNA • Translation of RNA nucleotides to amino acids • tRNA has to be “bilingual”

16. Amino acid attachment site C G G U U U U U C G U U Codon Amino acid Anticodon Translation of the Genetic Code • 3 nucleotide bases = 1 amino acid • Every group of 3 mRNA nucleotides = Codon • Corresponding triplet of bases on the tRNA = Anticodon

17. Second base C A U G UAU U UCU UUU UGU Cys Phe Tyr C UAC UGC UCC UUC Ser U UUA UCA Stop A A UAA Stop UGA Leu G UGG Trp UCG UUG Stop UAG U CAU CCU CUU CGU His CUC C CCC CGU CAC Leu Pro Arg C A CUA CCA CAA CGA Gln G CUG CGG CCG CAG First base Third base U AUU ACU AAU AGU Ser Asn AUC lle C ACC AAC AGC Thr A A AUA ACA AGA AAA Arg Lys Met or start G AUG AAG ACG AGG U GUU GCU GAU GGU Asp C GUC GCC GAC GGC G Val Gly Ala A GCA GUA GAA GGA Glu GUG GCG G GAG GGG GAG The mRNA to Amino Acid Dictionary • AUG =Start • UAA and UAG = Stop • The code is redundant: • Just as “drink” and “beverage” both represent • GCU and GCG both code for alanine

18. Translation Overview • Intitiation • Elongation • Termination

19. Met Anticodon U C A Codon G U A Translation • Intitiation • Initiator tRNA binds to START codon Amino acid tRNA rRNA mRNA

20. Amino acid Polypeptide Anticodon mRNA Codons Condon recognition mRNA movement Stop codon Peptide bond formation New peptide bond Translocation Translation • Elongation • Codon recognition • Peptide bond formation • rRNA also functions as an enzyme • Translocation

21. New peptide bond forming Growing polypeptide Elongation Codons mRNA Polypeptide Termination The ribosome recognizes a stop codon. The poly- peptide is terminated and released. Stop codon Translation • Termination • STOP codon on mRNA • Polypeptide (protein) is released

22. Summary Genotype • The DNA code that makes up a gene is transcribed into mRNA • rRNA brings mRNA and tRNA together • tRNA translates the code from nucleotides to amino acids • Newly made protein is released Phenotype