Chapter 8 From DNA to Proteins

1. Chapter 8From DNA to Proteins DNA rap

2. Look at the image of the mice below. Notice anything that seems odd? These mice have had a jellyfish gene (Green Fluorescent protein) inserted into their DNA by way of a virus. The virus inserted the GFP gene into the DNA of the mice.

3. What is DNA? In your own words, write down what DNA is

4. What is DNA? How does it transmit genetic information? What is the structure of DNA? These were all questions scientists raced to figure out from 1923 – the 1960’s. It was The Race for the Double Helix

5. There were a number of scientist who worked on trying to figure out what was the genetic material in a cell. Was it the proteins or the nucleic acids? They worked with bacteria and viruses as models and figured out that it was the nucleic acids that were responsible for passing on traits. Therefore, the DNA is the heredity material

6. Conclusion: Nonpathogenic mice were transformed by nucleic acid

7. Used S35 Used P32 Found that the S35stayed outside the cell & P32ended up in the bacteria and then in new viruses * • Conclusion: • DNA is the genetic material which is transmitted from one generation to the next

8. Erwin Chargaff – 1950 Noticed a pattern in the amounts of the four bases: Adenine, Guanine, Cytosine, and Thymine • Found the # of Guanine = # of Cytosine nitrogen bases in DNA • The # of Thymine = # of Adenine • Didn’t know why though!

9. What else did they know? Knew that: • DNA was a polymer made up of repeating units (monomers) called nucleotides • Nucleotides are made up of: • a 5 carbon sugar (called Deoxyribose) • a phosphate group • 4 different nitrogen bases P S

10. 4 Nitrogen Bases • Thymine (T) • Adenine (A) • Cytosine (C) • Guanine (G) Remember that the amount of Guanine = Cytosine and the amount of Thymine = Adenine

11. Label the diagram of the nucleotide below Phosphate group Nitrogen base Deoxyribose sugar Identify the 4 nitrogen bases in DNA 1. _________________ 2. _________________ 3. _________________ 4. _________________ Guanine Cytosine Adenine Thymine

12. The Main Characters in Cracking the Genetic Code Maurice Wilkins Watson & Crick Rosalind Franklin

13. Putting all the evidence together • Rosalind Franklin workedin Maurice Wilkins’ lab. • Purified, then crystallized DNA and then shot X-Rays through the crystal. • Took Photo 51 (100 hr exposure!!) • Showed that DNA was a double helix with the bases in a regular pattern inside the 2 twisting strands.

14. James Watson and Francis Crick • Model builders trying to figure out the structure of DNA. • Somehow, they saw Franklin’s Photo 51 • Immediately figured out the same thing that Franklin did but published faster than she did. • DNA was a double helix • Two twisting strands of alternating sugars and phosphates with the nitrogen bases inside • Win Nobel Prize along with Wilkins. (Franklin dies prior to the award).

16. Structure of DNADeoxyribonucleic acid It is a polymer of Nucleotides (monomer) 5 carbon sugar – deoxyribose A phosphate group A nitrogen base P S N-base Nucleotide Single nucleotide

17. DNA Model Lab • 24 deoxyribose sugars -S • 24 Phosphate groups -P • 6 of each of the following: • Adenine - A • Thymine - T • Cytosine - C • Guanine - G

18. DNA is a double helix with thesugarsand phosphate groups alternating along the sides rungs The nitrogen bases are paired together (following the base pairing rules) Guanine – Cytosine Adenine - Thymine

19. What holds DNA together? Covalent bonds • The alternatingSugarsand Phosphategroups are held together by covalent bonds • The nitrogen bases are attached to the sugar molecules by covalent bonds • The bond between the two nitrogen bases is a weak hydrogen bond. S S S S S S S S

20. Label the DNA strand shown to your right. 1. Put a P on each of the Phosphate groups 2. Put an S on each of the Sugars3. Using the base pairing rules, fill in the base pairs 4. Label the bond indicated by the arrow

21. DNA Model Lab You will need to cut out and label: 24 Phosphates - P 24 Deoxyribose – S 6 Adenine – A 6 Thymine – T 6 Cytosine – C 6 Guanine - G

22. Need for more DNA We have over 100 trillion cells. Each cell has exactly the same DNA in its nucleus except for the gametes (sex cells) DNA needs to be replicated EXACTLY each time a new cell is produced during Interphase of Mitosis Watson and Crick looked at the structure of DNA and figured out how it could make a copy of itself “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material”.

23. Why would a zipper be a good analogy to DNA? • DNA and a zipper have two strands • The teeth of the zipper are like the nitrogen bases of DNA • The teeth are held together by a bond like the Hydrogen bonds holding the bases together

24. If you wanted to make an exact copy of DNA, how would you do it precisely and quickly?

25. The process of making an exact copy of DNA is called DNA Replication As a result of Replication, there will be two identical strands of DNA The two strands of DNA act as templates for the new strands.

26. DNA Replication Original DNA strand Hydrogen bonds are broken between the bases exposing the base New DNA nucleotides bind with the exposed bases, following the base pairing rules Two identical strands of DNA are produced with the old strand on the outside of each new strand

28. How does DNA Replication occur? • The DNA helix needs to flatten out • No one likes a twisted zipper • In order to expose the nitrogen bases, the helix needs to be unzipped by Helicase. The hydrogen bonds are broken, exposing the bases. • Just like the slide on a zipper exposes the teeth • An enzyme called DNA polymerase “re-zips” the two strands by allowing free DNA nucleotides in the nucleus to bond to the exposed bases on both sides of the helix

29. The helix is being flattened The hydrogen bonds are being broken by Helicase

31. In the space below, write out the 3 steps in DNA Replication 2. 3. Animation Glenn Here is a song Maybe you will like this one better

32. It’s your turn to Replicate DNA Original DNA strand DNA being replicated New DNA strands following replication C – G A – T T – A G – C C – G C – G T – A T – A A – T G – C C – G A – T T – A G – C C – G C G T-__ __-A T-__ __-A A-__ __-T G-__ __-C C – __ A – __ T – __ G – __ C – __ C – __ T – __ T – __ A – __ G – __ __ – G __ – T __ – A __ – C __ – G __ – G __ – A __ – A __ – T __ – C

33. Listen to the song and then explain what DNA’s real job is?Central Dogma Song What is DNA’s job? Francis Crick figured out that the role of DNA in the production of proteins. He called this the Central Dogma. DNA to RNA, RNA to Proteins

34. The Production of Proteinsis called Protein Synthesis Remembering back to the cell, where in a cell does Protein Synthesis take place? Occurs in the Ribosomes of all cells, both prokaryotic (bacterial) and eukaryotic Protein Amino acid Ribosome tRNA mRNA Ribosome

35. Big problem with DNA and Protein Synthesis We have always referred to DNA as the Boss The DNA (Boss) stays in its office – the nucleus. Only problem is that the DNA is too large to get out of the nucleus. DNA has the message (gene) to produce a particular protein. Since it can’t deliver the message itself, it needs a messenger to deliver the message to the ribosomes. It also can’t make the protein itself from available amino acids in the cytoplasm so it needs some molecule to transfer the amino acids to the ribosomes to make the protein.

36. RNA Ribonucleic acidThe other Nucleic Acid Acts as a messenger between DNA and the ribosomes and carries out protein synthesis by delivering the amino acids to the ribosome

37. How DNA & RNA Differ • RNA is single stranded. DNA is double stranded • Has Ribose sugar instead of Deoxyribose • Can be found in the nucleus, cytoplasm or at the ribosomes DNA is only in the nucleus • Contains Uracil in place of Thymine so Adeninebonds with Uracil

38. Three different kinds of RNA • Messenger RNA (mRNA) Is produced in the nucleus of eukaryotes and gets DNA’s message. Then goes to the ribosomes • Transfer RNA (tRNA) Found in the cytoplasm & transfers amino acids to the mRNA in the ribosomes • Ribosomal RNA (rRNA) Makes up the ribosomes

39. Label the three types of RNA and tell what each of them does mRNA tRNA rRNA

40. Steps in Protein Synthesis • Transcription DNA’s message on the gene gets “read” (in reverse) by messenger RNA (mRNA). • RNA polymerase enzyme will allow free RNA nucleotides to temporarily bind to DNA • Thismessage on mRNA will go to the ribosomes. • Translation mRNA will attach into the ribosomes and amino acids will be transferred in the proper order according to the gene by transfer RNA (tRNA) • The amino acids will string together to form a protein (polypeptide)

41. Transcription • Occurs in the nucleus: • If DNA is: ATG CCG TTA GAC CGT TGA • TAC GGC AAT CTG GCA ACT • mRNA is: AUG CCG UUA GAC CGU UGA • (Remember, U substitutes for T in RNA) • This is called Transcription. Animation

42. mRNA

43. What happens in transcription?

44. Translation Process that converts a mRNA message into a polypeptide mRNA will now go to the ribosomes mRNA has the reverse code for DNA’s gene. Remember that DNA’s genes code for proteins and proteins are made up of amino acids Now we must consult the Genetic Code decoding wheel

45. Going off of the mRNA’s codons, we use this to figure out which amino acid is needed (according to DNA’s message) Stop Codons The Genetic Code Try: GGG: ____________ CAU: ____________ AUG: ____________ UUU: ____________ GAC: ____________ UAG:____________ Start codon

46. Try: GGG: ____________ CAU: ____________ AUG: ____________ UUU: ____________ GAC: ____________ UAG:____________

47. mRNAis: AUG CCG UUA GAC CGU UGA tRNAwill bind with specific amino acids and transfer them to the codon (3 bases in a row on mRNA) mRNAis: AUG CCG UUA GAC CGU UGA Amino acid: Methionine (start codon) Proline Leucine Aspartic Acid Arginine Stop codonmeans to stop translation

48. Every 3 consecutive bases on mRNA is a codon. CUA AAU GAU • tRNA with the anticodon (complimentary to mRNA) links to mRNA. It carries a specific Amino Acid (specified by mRNA). ***ALWAYS DECODE OFF OF mRNA!!!!!!*** If DNAreads:T A C G T C G A T T G G CAA… mRNA: A U G C A G C U A ACC GUU… tRNA: U A C G UC G A U UGG CAA… Translation: Amino Acids: Methionine - Glutamine – Leucine -Threonine – Valine Please note that DNA’s code and tRNA match!! Translation!!!!!

49. When adjacent Amino Acids link together, they link together with a peptide bond and form a Polypeptide (protein). Peptide bonds Amino acid Growing Polypeptide Animation

50. DNAmRNAProtein TranscriptionTranslation Protein Synthesis