1 / 56

QOD 1/3/12

QOD 1/3/12. What is the shape of DNA?. Double Helix. DNA, RNA, and Protein Synthesis. Discovery of DNA. 1928- Fredrick Griffith

tallulah-raymond
Download Presentation

QOD 1/3/12

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. QOD 1/3/12 • What is the shape of DNA? Double Helix

  2. DNA, RNA, and Protein Synthesis

  3. Discovery of DNA • 1928- Fredrick Griffith • He found that when harmless bacteria are mixed with dead harmful bacteria, the harmless will absorb the genetic material of the harmful and become harmful themselves • Transfer of genetic material is called transformation

  4. Discovery of DNA • 1940s- Avery and colleagues • Wanted to know what caused transformation (DNA, RNA, or protein) • They separated these individual parts and tested them. • They found DNA was the cause of transformation • In other words, they found if harmless bacteria took in harmful bacteria’s DNA, the harmless became harmful.

  5. Discovery of DNA • 1952- Hershey and Chase • Wanted to test whether DNA or protein was the genetic material that viruses pass on when they infect an organism. • They used viruses that infect bacteria (called bacteriophages) • They radioactively labeled the DNA and the protein (this allowed them to trace the path of each) • They found DNA was injected into the bacteria to infect it, not protein. So DNA was the genetic material

  6. Discovery of DNA • 1950s- Watson, Crick, Franklin, and Wilkins • Franklin and Wilkins discover DNA is helical • Watson and Crick build a model of DNA and determine it is a double helix

  7. DNA Structure • DNA is a double helix

  8. DNA Structure • It is made of nucleotides (so nucleotides are the monomers of DNA!) • Nucleotides have 3 parts: • Nitrogenous base (there are 4 kinds) • Phosphate Group • 5 carbon sugar called deoxyribose

  9. One Strand of DNA phosphate deoxyribose bases nucleotide

  10. DNA Structure • Nitrogenous bases: • Contain nitrogen and is a base • Purines- (double ringed) • Adenine (A) • Guanine (G) • Pyrimadines- (single ringed) • Cytosine (C) • Thymine (T)

  11. DNA Structure • DNA is made up of 2 straight chains of nucleotides • The bases on each of those chains are attracted to each other and form hydrogen bonds • The force of thousands or millions of hydrogen bonds keeps the two strands of DNA held tightly together

  12. DNA Structure • If DNA was a spiral staircase… • The alternating sugar and phosphates would be the hand rails. • The bases would be the steps • But, they would be weak steps as they are only held together by hydrogen bonds

  13. DNA models • Since the sugar-phosphate “hand rails” of DNA never change, we often simplify DNA into the letters of the nitrogenous bases. • For example, this DNA strand can be simplified to… TGAC ACTG

  14. DNA Structure • Base pairing rulesin DNA: • Hydrogen bonds form between specific pairs • Adenine ALWAYS pairs with Thymine • Cytosine ALWAYS pairs with Guanine • These pairs (A-T and C-G) are called complementary base pairs • Each complimentary pair contains one single and one double ringed base

  15. DNA Structure • Because of the base pairing rules, one strand of DNA is complementary to the other strand (otherwise they would not stick together!) • So if one strand has a base sequence of TGCC, the other strand will have ACGG.

  16. Let’s Practice • Right the complimentary DNA strand for… TGACCGAT ACTGGCTA

  17. QOD 1/4/12 • Which scientists built the first model of DNA? Watson and Crick

  18. DNA Replication • DNA Replication is the process by which DNA is copied in a cell before the cell divides.

  19. DNA Replication • First, enzymes called Helicases separate the two strands of DNA • Helicases break hydrogen bonds

  20. DNA Replication • Next, enzymes called DNA polymerases add complimentary nucleotides to the separated strands of DNA • Nucleotides are found floating freely in the nucleus

  21. DNA Replication • When replication is finished, there are 2 DNA molecules, each had one old strand and one new strand

  22. DNA Replication • Replication is usually very accurate • There is only about 1 error for every BILLION nucleotides added! • The reason is that DNA Polymerases also “proofread” the DNA and fix any errors during replication

  23. DNA Replication • If an error does occur, it results in a different nucleotide sequence in the new DNA strands • This is called a mutation • A change in even one nucleotide can be very harmful to an organism (for reasons we will see later) • Some mutations can affect the growth of cells, causing growth to accelerate, this results in cancer • Changes can be good- mutations sometimes lead to adaptations and therefore evolution

  24. Protein Synthesis • DNA is the “code” for hereditary characteristics. • The genetic code is how organisms store hereditary information and translate it into proteins

  25. Protein Synthesis • DNA codes for all of the bodies proteins (like enzymes) • Genes are sequences located in the DNA that code for specific characteristics • The code (or gene) for the production of the protein melanin is in your DNA and creates your hair and skin color • The code or recipe for all of the enzymes that help you digest your food is located in your DNA

  26. Protein Synthesis • The “code” or “recipe” within DNA cannot be read directly- • DNA cannot leave the nucleus and proteins are made in the cytoplasm of cells • So the code is transcribed (copied) and translated (turned into something useful) by ribonucleic acid (RNA)

  27. Protein Synthesis • Remember, proteins make us who we are • They are responsible for chemical reactions occurring in us (enzymes) and for the hereditary characteristics that we have (such as eye color) • The building blocks (or monomers) of proteins are amino acids • DNA holds the recipe for the amino acid sequence of all the proteins we need to make

  28. Protein Synthesis • RNA directs protein synthesis, which is the making of proteins from DNA

  29. DNA vs RNA • Both are made of nucleotides • Both are involved in protein synthesis • DNA has the sugar deoxyribose, while RNA has the sugar ribose • RNA uses the nitrogenous base uracil instead of thymine (used in DNA) • RNA is single stranded, while DNA is double stranded • RNA is usually MUCH shorter than DNA

  30. Protein Synthesis • There are several types of RNA involved in protein synthesis • Messenger RNA (mRNA) – carries the genetic instructions from the DNA to the ribosomes

  31. Protein Synthesis • Ribosomal RNA (rRNA) – part of the ribosome • Remember ribosomes make proteins Anticodon Codon mRNA

  32. Protein Synthesis Amino Acid • Transfer RNA (tRNA) – transfers the amino acids to the ribosomes to make proteins Anticodon

  33. QOD 1/6/12 • What type of RNA carries the genetic instructions from the DNA to the ribosomes? mRNA

  34. Protein Synthesis - Transcription • The first step in protein synthesis is transcription: • An Enzyme called RNA polymerase binds to a genes promoter region • A promoter is just a specific nucleotide sequence where the RNA polymerase can attach • The RNA attaches to the RNA polymerase and the DNA begins to uncoil

  35. Protein Synthesis - Transcription • The RNA polymerase adds complimentary nucleotides resulting in a straight chain RNA molecule • The DNA code determines what bases will be added (A with U, T with A, and G with C) • For example if the DNA code for a gene is ATCCGTT, then the RNA will be UAGGCAA • Remember, RNA does not have thymine, it has Uracil!!

  36. Protein Synthesis - Transcription • The copying of DNA continues until the RNA polymerase reaches a STOP signal • That is a specific sequence of nucleotides that tells the RNA polymerase to “STOP” and release the RNA and DNA • The RNA is mRNA, because it is the messenger of the “code” from the DNA to the ribosomes

  37. Let’s Practice • What is the mRNA strand for the following DNA sequences?? • DNA - ATCGGT • mRNA - UAGCCA

  38. Let’s Practice • What is the DNA sequence that the following mRNA strands came from?? • mRNA - GUCAUG • DNA - CAGTAC

  39. Protein Synthesis - Translation • Once the newly made RNA leaves the nucleus it attaches to a ribosome at the promoter region. • Ribosomes will “read” 3 nucleotides in the RNA code at a time • These 3 nucleotides are called codons. • Each Codon codes for an amino acid, a START signal, or a STOP signal

  40. Protein Synthesis - Translation • For example, the sequence AUG codes for the amino acid Methionine and means START (it is the only one that means start) • ALL mRNA molecules start with AUG, otherwise, they would have a start region for protein synthesis

  41. Protein Synthesis - Translation • So, in translation, the RNA is translated into amino acids, which are put together to form proteins (or polypeptides) • The translation occurs with the help of tRNA, which carries the amino acids

  42. Protein Synthesis - Translation • When the ribosome reads the start sequence (AUG), a tRNA molecule comes along with the anticodon • The anticodon is the complementary sequence, which would be UAC. • The complementary bases bond with each other and the amino acid methionine begins the protein synthesis within the ribosome • tRNA transfers amino acids to the ribosome

  43. Protein Synthesis - Translation • There are only 20 amino acids • Most amino acids have more than on codon • For example, Leucine’s codons are UUA, UUG, CUU, CUC, CUA, and CUG • But each codon codes for ONLY 1 amino acid • For example, CUU only codes for Leucine and nothing else

  44. Protein Synthesis - Translation • After the start sequence, the ribosome moves to the next codon. • Let’s say the next codon is GUC • Now a tRNA that has the anticodon CAG would attach to the ribosome and it would carry the amino acid Valine. • The amino acid Valine would attach to the Methionine from before (now we have a dipeptide!)

  45. Protein Synthesis - Translation • This process continues and the polypeptide grows until the STOP codon is reached • UAA, UAG, and UGA are the only stop codons • The protein, ribosome and all RNA is released to perform other needed functions

  46. Protein Synthesis - Summary • Let’s learn how to BREAK THE CODE!!

  47. Protein Synthesis - Summary • This is an mRNA strand- figure out what the DNA code was that it came from:

  48. Protein Synthesis - Summary • 1 - TAC • 2 - TGC • 3 - CTC • 4 - GAA • 5 - GCC • 6 - TCG • 7 - ATC

  49. Amino Acid Anticodon Protein Synthesis - Summary • Now figure out the anticodons (which will be found on the tRNA)

  50. Protein Synthesis - Summary • 1 - UAC • 2 - UGC • 3 - CUC • 4 - GAA • 5 - GCC • 6 - UCG • 7 - AUC

More Related