1 / 31

DNA replication/Protein synthesis

DNA replication/Protein synthesis. Chapters 14 and15. Eukaryotic DNA Replication. The larger size and complex packaging of eukaryotic chromosomes means they must be replicated from multiple origins of replication.

kaethe
Télécharger la présentation

DNA replication/Protein synthesis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. DNA replication/Protein synthesis Chapters 14 and15

  2. Eukaryotic DNA Replication The larger size and complex packaging of eukaryotic chromosomes means they must be replicated from multiple origins of replication. The enzymes of eukaryotic DNA replication are more complex than those of prokaryotic cells.

  3. Eukaryotic DNA Replication Synthesizing the ends of the chromosomes is difficult because of the lack of a primer. With each round of DNA replication, the linear eukaryotic chromosome becomes shorter.

  4. Eukaryotic DNA Replication telomeres – repeated DNA sequence on the ends of eukaryotic chromosomes • produced by telomerase telomerase contains an RNA region that is used as a template so a DNA primer can be produced

  5. Clicker • Summary of DNA replication

  6. How genes work • Function of genes • Protein Synthesis

  7. The Nature of Genes Beadle and Tatum proposed that each enzyme of the arginine pathway was encoded by a separate gene. They proposed the one gene – one enzyme hypothesis. Today we know this as the one gene – one polypeptide hypothesis.

  8. The Nature of Genes The central dogma of molecular biology states that information flows in one direction: DNA RNA protein Transcription is the flow of information from DNA to RNA. Translation is the flow of information from RNA to protein.

  9. The Genetic Code Deciphering the genetic code required determining how 4 nucleotides (A, T, G, C) could encode more than 20 amino acids. Francis Crick and Sydney Brenner determined that the DNA is read in sets of 3 nucleotides for each amino acid.

  10. The Genetic Code codon: set of 3 nucleotides that specifies a particular amino acid reading frame: the series of nucleotides read in sets of 3 (codon) • only 1 reading frame is correct for encoding the correct sequence of amino acids

  11. The Genetic Code stop codons: 3 codons (UUA, UGA, UAG) in the genetic code used to terminate translation start codon: the codon (AUG) used to signify the start of translation The remainder of the code is degenerate meaning that some amino acids are specified by more than one codon.

  12. Gene Expression Overview template strand: strand of the DNA double helix used to make RNA coding strand: strand of DNA that is complementary to the template strand RNA polymerase: the enzyme that synthesizes RNA from the DNA template

  13. Gene Expression Overview Transcription proceeds through: • initiation – RNA polymerase identifies where to begin transcription • elongation – RNA nucleotides are added to the 3’ end of the new RNA • termination – RNA polymerase stops transcription when it encounters terminators in the DNA sequence

  14. Gene Expression Overview • Translation proceeds through • initiation – mRNA, tRNA, and ribosome come together • elongation – tRNAs bring amino acids to the ribosome for incorporation into the polypeptide • termination – ribosome encounters a stop codon and releases polypeptide

  15. Gene Expression Overview Gene expression requires the participation of multiple types of RNA: messenger RNA (mRNA) carries the information from DNA that encodes proteins ribosomal RNA (rRNA) is a structural component of the ribosome transfer RNA (tRNA) carries amino acids to the ribosome for translation

  16. Eukaryotic Transcription RNA polymerase Itranscribes rRNA.

  17. tRNA and Ribosomes tRNAmolecules carry amino acids to the ribosome for incorporation into a polypeptide • aminoacyl-tRNA synthetasesadd amino acids to the acceptor arm of tRNA • the anticodon loop contains 3 nucleotides complementary to mRNA codons

  18. tRNA and Ribosomes The ribosome has multiple tRNA binding sites: • P site – binds the tRNA attached to the growing peptide chain • A site – binds the tRNA carrying the next amino acid • E site – binds the tRNA that carried the last amino acid

  19. tRNA and Ribosomes The ribosome has two primary functions: • decode the mRNA • form peptide bonds

  20. When things go wrong • Mutations

  21. Mutation: Altered Genes Point mutations alter a single base. • base substitution mutations – substitute one base for another • transitionsor transversions • also called missense mutations • nonsense mutations – create stop codon • frameshift mutations – caused by insertion or deletion of a single base

  22. Group activity • Visually construct a model of DNA replication and protein synthesis. Use separate pieces of paper for each enzyme and nucleotide so that you can manipulate the system to demonstrate a point mutation.

  23. Clicker • Summary

  24. Cell Cycle • Mitosis • Meiosis

More Related