1 / 35

Protein Synthesis

Protein Synthesis. 3 major processes: Replication → DNA copied to form 2 new DNA molecules Nucleus Transcription → DNA info copied to RNA Nucleus Translation → building a protein according to RNA instructions Cytoplasm. RNA & Transcription. From Gene to Protein

oksana
Download Presentation

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. Protein Synthesis • 3 major processes: • Replication→ DNA copied to form 2 new DNA molecules • Nucleus • Transcription → DNA info copied to RNA • Nucleus • Translation → building a protein according to RNA instructions • Cytoplasm

  2. RNA & Transcription From Gene to Protein (DNA  RNA  Protein) Honors Biology Ms. Kim

  3. The Flow of Genetic Information • DNA • information in a specific sequence (order) of nucleotides along 2 DNA strands • Leads to specific traits by controlling the synthesis of proteins • Gene expression includes two stages • Transcription: DNA  RNA • “transcribe” = to copy into another form • Translation: RNA polypeptide (proteins) • “translate” = to change into another language

  4. What is transcription? • Process of copying DNA (the template strand) into a complementary RNA strand • Occurs in the nucleus • Similar to DNA replication, but Uracil (U) replaces Thymine (T)

  5. Why RNA? • RNA – Ribonucleic Acid • How does DNA get out of the nucleus and go to the ribosomes where the proteins are made? • It can’t! DNA cannot leave the nucleus! • So, it copies itself into RNA and that leaves and goes to the ribosomes • EXAMPLE – library book, photocopy

  6. What are the characteristics of RNA? • Ribose Nucleic Acid • Single stranded • Made of sugars (called ribose), phosphate groups and nitrogen bases • Backbone= alternating ribose sugar/phosphates held together by PHOSPHODIESTER BONDS • Made of RNA nucleotides • Contains bases: • (A) Adenine • (G)Guanine • (C) Cytosine • (U) Uracil (replaces Thymine)

  7. DNA vs. RNA: • Sugars = • DNA – deoxyribose • RNA – ribose • Nitrogen bases = • DNA – A, C, G and thymine (T) • RNA – A, C, G and uracil (U) • Location = • DNA – inside nucleus only • RNA – in and out of nucleus • Stranded = • DNA – Double stranded • RNA – Single stranded

  8. Messenger RNA • mRNA copies the DNA code and carries it into the cytoplasm where protein synthesis happens • Notice how the bases of mRNA are organized into codons • A codon consists of 3 consecutive bases  code for a specific amino acid • Remember a chain of amino acids = a protein • So….DNA codes for proteins!

  9. The Ribosome • Part of cell where translation (protein synthesis) occurs • Where proteins are actually made

  10. Basic Principles of Transcription and Translation • Transcription • the synthesis of RNA from DNA (DNA  mRNA) • Produces messenger RNA (mRNA) • Occurs in the nucleus of eukaryotes and nucleoidregion of prokaryotes • Translation (happens later) • actual synthesis of a polypeptide • mRNA  polypeptide  protein • Occurs on ribosomes

  11. DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide Prokaryotic cell. In a cell lacking a nucleus, mRNAproduced by transcription is immediately translatedwithout additional processing. In prokaryotes, transcription and translation occur together

  12. Nuclear envelope DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA Ribosome TRANSLATION Eukaryotic cell. The nucleus provides a Separate compartment for transcription. The original RNA transcript, called pre-mRNA, is processed in various ways before leaving the nucleus as mRNA. Polypeptide (b) In eukaryotes, pre mRNA transcriptsare modified (changed) before becoming true “mature” mRNA “Transcript” is a fancy word for “message”

  13. How is Protein Made? • Cells are controlled by a cellular chain of command • DNA RNA protein • Called the “Central dogma of biology” • What are proteins made out of? • Amino acids • There are 20 different amino acids • building blocks of proteins • All living things use the same 20 amino acids to make proteins!!!

  14. The Genetic Code • It’s a table used that TRANSLATES RNA nucleotides (or mRNA “letters”) into one of the 20 amino acids • 3 letter mRNA “word” = 1 amino acid • There are 4 different RNA “letters” that can be used • A, U, C, and G

  15. Codons: Triplets of Bases • Genetic information is coded as a sequence ofbase triplets, or codons • 3 letter mRNA “words” = codon • FOUND ONLY ON mRNA • Codons must be read in the correct order • For specified polypeptide to be produced • Always read in the 5’  3’ direction

  16. THE GENETIC CODE

  17. Evolution of the Genetic Code • The genetic code is nearly universal • Shared by organisms from the simplest bacteria to the most complex animals • All organisms have SAME DNA “letters” and SAME RNA “letters”

  18. Gene 2 DNA molecule Gene 1 Gene 3 DNA strand (template) 5 3 A C C T A A A C C G A G TRANSCRIPTION A U G G G G C U C U U U mRNA 5 3 Codon TRANSLATION Protein Gly Phe Ser Trp Amino acid Figure 17.4 During transcription, a gene determines the sequence of bases along length of mRNA.

  19. Transcription • DNA  RNA • RNA synthesis is done by RNA polymerase • Forces DNA strands apart (breaks H bonds btw bases) and hooks together RNA nucleotides • Follows same DNA base-pairing rules, except in RNA, uracil substitutes for thymine • A = U (T on DNA = A in RNA) • C = G

  20. Synthesis of an RNA Transcript • Initiation • DNA strands unwind • RNA polymerase initiates mRNA synthesis at start point on templates called promoters • RNA polymerase binds to promoter • Elongation • RNA polymerase moves downstream, unwinding DNA & elongating mRNA transcript 5 3 direction • In wake of transcription, DNA strands re-form a double helix. • Termination • mRNA transcript is released at terminator signal • RNA polymerase detaches from the DNA

  21. RNA Polymerase Binding and Initiation of Transcription • Promoters (on DNA) starts RNA synthesis (BOTH prokaryotes & eukaryotes) • RNA polymerase binds here then unwinds DNA • RNA Polymerase adds new FREE RNA nucleotides to DNA template strand in 5’ 3’ direction • “TATA box” = start signal on DNA promoter • Determines which strand is used as template  only 1 side is used at a time!

  22. Transcription Animation • http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

  23. Elongation Non-template strand of DNA RNA nucleotides RNA polymerase T A C C A T A T U 3 C 3 end T G U A G G A G E A C A C C 5 A A T A G G T T Direction of transcription (“downstream”) 5 Template strand of DNA Newly made RNA

  24. Intron 5 3 5 Cap Poly-A tail TRANSCRIPTION DNA Exon Pre-mRNA RNA PROCESSING Introns cut out and exons spliced together Coding segment mRNA Ribosome TRANSLATION mRNA 5 Cap Poly-A tail Polypeptide 1 146 3 UTR 5 UTR Split Genes and RNA Splicing • RNA splicing and RNA Modification • Removes introns and joins exons • Introns = non-coding regions • Exons = coding regions that EXIT nucleus Intron Pre-mRNA Exon Exon Mature mRNA Figure 17.10

  25. 3 1 2 RNA transcript (pre-mRNA) 5 Intron Exon 1 Exon 2 Protein Other proteins snRNA snRNPs Spliceosome 5 Spliceosome components Cut-out intron Mature mRNA 5 Exon 1 Exon 2 RNA splicing is carried out by spliceosomesin some cases Called small nuclear RNA + proteins (ribonucleoproteins)

  26. mRNA CodonsLets Practice:CCAAGAGUGUGAAUG

  27. Practice Coding • DNA Complementary – A T C • DNA Template - A G A • mRNA - U A G • Amino Acid Seq- Ile-Ser-Stop T C T TAG ATC T A G A U C U C U

More Related