1 / 34

DNA

Human Development. Gene Therapy. DNA Fingerprinting. Evolution. DNA. Cloning. Genetic Diseases. Individualism. Human Genome Project. THE BIG PICTURE. DNA is the recipe for Life. Each person has a unique sequence of DNA Each person to have a unique collection of proteins

keelie-holmes
Download Presentation

DNA

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. Human Development Gene Therapy DNA Fingerprinting Evolution DNA Cloning Genetic Diseases Individualism Human Genome Project

  2. THE BIG PICTURE DNA is the recipe for Life Each person has a unique sequence of DNA Each person to have a unique collection of proteins Each person having a unique appearance and behavior which causes which contributes to

  3. Imagine that the genome is a book… • There are 23 chapters called CHROMOSOMES • Each chapter contains several thousand stories called GENES • Each story is made up of paragraphs called EXONS, which are interrupted by advertisements called INTRONS • Each word is written in letters called BASES

  4. Proteins which are linear sequences of amino acids DNA contains a linear base code that… G - C Amino acid T - A Controls production of… C - G Amino acid A - T A - T Amino acid

  5. Three nucleotides in DNA code for one amino acid in a protein Sequence of bases in DNA are read as triplet codes codes for C G C T A A C G A Amino acid Amino acid Amino acid

  6. From Gene to Protein:Part 1 – Transcription Making mRNA Chapter 17 A-B

  7. Garrod (1909) • 1st to suggest genes dictate phenotypes via enzymes that catalyze certain cell reactions • “Inborn error of metabolism” • Have a disease = cannot make an enzyme • i.e. Alkaptonuria • Proteins seem to be the link between genotype and phenotype!!!

  8. Biochemistry Arises (1930s) • Degradation and creation of organic molecules in cells through metabolism • Catalyzed by specific enzymes • i.e. eye color pigments in fruit flies

  9. Beadle and Tatum (1930s) • Studied a type of bread mold (Neurospora crassa) • Wild type: synthesized organic molecules from minimal salts media • Mutant: made by x-rays – could not survive b/c could not make these molecules • Hypothesized that 1 gene creates 1 enzyme • In this case, enzyme needed to catalyze a reaction to make molecules for survival

  10. Figure 17.1 Beadle and Tatum’s evidence for the one gene-one enzyme hypothesis

  11. 1 gene, 1 enzyme • This theory revised over and over again • Now: 1 gene, 1 polypeptide • b/c not all enzymes are proteins

  12. DNA vs. RNA

  13. DNA vs. RNA

  14. So how exactly are proteins made? DNA  RNA  Polypeptide  Protein  Phenotype Transcription Translation Modification Expression

  15. DNA & PROTEIN SYNTHESIS

  16. TRANSCRIPTION • Process of using DNA as template to create RNA (message) • RNA is not identical to DNA • It is complementary b/c of base-pairing rules

  17. Steps of Transcription • Initiation • Initiation complex binds to DNA at specific sequence • Elongation • Creation of pre-mRNA • Termination • Release of pre-mRNA

  18. What is RNA polymerase? • Enzyme that pries DNA apart and puts together RNA nucleotides as it moves along DNA template • Moves 3’ – 5’ of template • 5’ – 3’ RNA growth • In prokaryotes – there is only 1 RNA polymerase • In eukaryotes – RNA Polymerase II does this

  19. TRANSCRIPTION: INITIATION • Promoter – RNA polymerase binds to this site, upstream from terminator • Contains sequences for • RNA polymerase to bind • Which strand of DNA is the template • Where transcription begins on DNA • TATA box and TATA Binding Protein • In eukaryotes: transcription factors must help RNA polymerase II bind to promoter • In prokaryotes: RNA polymerase binds itself

  20. TATA Box • 5’ TATAAA 3’ (or some variant) • 3+ adenine bases • 25-35 bp upstream of transcription site • TATA Binding Protein (TBP) • Helps unwind helix • Easy b/c 2 hydrogen bonds • About 50% promoters lack TATA box • But they have “initiator element” or “downstream core promoter” • And still use TBP

  21. Eukaryotic Transcription Factors • Collection of proteins that help RNA polymerase II bind to DNA template and start transcription • After these proteins bind and RNA polymerase binds to DNA, it is called the Transcription Initiation Complex

  22. TRANSCRIPTION: ELONGATION • RNA polymerase moves along DNA template • Adding RNA nucleotides • Remember SUGARS!!! • DNA double helix reforms as RNA polymerase 3’-5’ • New RNA strand peels from DNA

  23. Several Proteins at Once! • Cells can increase the production of proteins at one time, using the same gene • Several RNA strands made using the same gene • RNA polymerases follow each other down DNA strand much like cars on highway

  24. TRANSCRIPTION: TERMINATION • Termination sequence in DNA • RNA polymerase “stops” transcribing • In prokaryotes – polymerase usually stops right after the signal, leaves and DNA closes • In eukaryotes – polymerase continues transcribing several 100 bases past stop signal • AAUAAA pre-mRNA end • Polymerase continues about 10-35 bases after this signal

  25. Eukaryotic Post-Transcriptional Modifications • 5’ cap • GTP added • Protection of mRNA from degradation • Signal for ribosome attachment in cytoplasm • 3’ end • Poly(A) tail • 50-250 Adenine nucleotides • Protection from degradation • May help export mRNA from nucleus

  26. Eukaryotic Post-Transcriptional Modifications: RNA Splicing • Non-coding segments interspersed between coding segments of pre-mRNA • Therefore, need to be spliced out • Introns – “intervening segments” • Specific sequence codes surround introns for splicing to occur (“GU/AG” rule) • Exons – “expressed segments” • Spliced back together once introns are taken out to make final mRNA

  27. Why do we have introns? • Regulatory roles in cell • Some genes are “coding” • Control mRNA to leave nucleus • Same gene – more than one polypeptide • Alternative RNA splicing • Facilitate evolution of new and potentially useful proteins • Increase potentially beneficial cross over or more places for cross over, leading to new proteins

  28. How does splicing occur? • Spliceosome • snRNPs – small nuclear ribonucleoproteins • pronounced “snurps” • Made of protein and RNA • snRNA – thought to have catalytic activity • Proteins – ones in snRNPs and other proteins • Cuts specific sites (GU/AG) and rejoins exons

  29. Spliceosomes – oval shaped • Bar = 50nm

  30. Final mRNA Produced • Every 3 nucleotides codes for 1 amino acid • Start, stop, and 20 aa • Codon • Leaves nucleus (polyA to 5’ cap) • Cytoplasm and recruits ribosomal subunits

  31. Figure 17.4 The dictionary of the genetic code

  32. Code evolved early in life • Code is nearly universal • Simplest bacteria to complex plants and animals • Present in common ancestors • Few exceptions • Paramecium, chloroplasts, and mitochondria • Genes can be transcribed and translated after they are transplanted from one species to another • Insert human insulin gene into bacteria

More Related