DNA, RNA & Protein Synthesis

1. DNA, RNA & Protein Synthesis Ribose RNA Hydrogen bonds Mrs. Stewart Biology I Uracil Adenine

2. Objectives over next few lessons: • Can differentiate between DNA and RNA • Can explain steps of Transcription • Can explain steps of Translation • Can summarize how to get from DNA code to the expression of a trait • Can summarize the relationship between chromosomes, genes and DNA

3. Face Partners

4. What is the relationship between chromosomes, DNA and genes • A gene is a section of the DNA sequence that codes for a protein. • Each unique gene has a unique sequence of bases. • This unique sequence of bases will code for the production of a unique protein. • It is these proteins and combination of proteins that determine the phenotypes for our traits.

5. What is the purpose of the genetic code in DNA? To create proteins

6. Objective: Be able to explain how we get from DNA code to expression of a trait DNA Gene Trait Protein

7. Bacon – explain the purpose of the DNA code

8. Central Dogma • The basic idea of how hereditary information flows from DNA sequence to create functioning proteins

9. Where is the DNA kept inside a cell? Inside the nucleus

10. Which organelle is the site of protein synthesis? Ribosomes

11. DNA cannot leave the nucleus, so…

12. DNA GENE RNA Ribosome Protein Trait

13. Two Types of Nucleic Acids • DNA – Deoxyribonucleic acid • RNA – Ribonucleic acid • Need both types of nucleic acids to get from the DNA code to producing proteins

14. RNA DNA Single Stranded & short (one gene) Double Stranded & long (1000s genes) Base Pairs: A-T C-G Base Pairs: A-U C-G Sugar: Ribose Sugar: Deoxyribose

15. RNA’s JOB = Use DNA code to make proteins!! Differences between DNA and RNA:

16. Eggs – tell bacon how to differentiate between DNA and RNA

17. Types of RNA Short single strand that carries a copy of the DNA code for one gene from the nucleus to the ribosome • mRNA – Messenger RNA • rRNA – Ribosomal RNA • tRNA – Transfer RNA Combines with proteins to make the ribosome. Carries amino acids to the ribosome to build a protein chain.

18. What does every gene “code” for? Proteins

19. What are the monomers that build proteins? Amino Acids

20. How do we read the DNA code? • To crack the genetic code found in DNA we need to look at the sequence of bases. • The sequence of bases are read in triplets (sets of 3) called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C • Each codon codes for a specific amino acid

21. Protein Synthesis Overview There are two steps to making proteins (protein synthesis): 1) Transcription (occurs in the nucleus) DNA RNA 2) Translation (occurs in the cytoplasm) RNA  protein

22. Protein Synthesis Animation • Protein Synthesis Overview Animation • Amoeba Sisters – protein synthesis • Teacher’s pet – protein synthesis

23. Adenine (DNA and RNA) Cytosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA Transcription Nucleus

24. Transcription occurs in three main steps:

25. Initiation: Transcription begins when the enzyme RNA polymerase binds to the DNA at a promoter site. Promoters are signals in the DNA strand (a certain sequence of bases) that indicate to the enzyme where to bind to make RNA.

26. Elongation: • The enzyme separates the DNA strands by breaking the hydrogen bonds, and then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA. • RNA polymerase pairs up free floating RNA nucleotides with DNA template and joins the nucleotides together to form the backbone of the new mRNA strand.

27. Termination When mRNA hits a termination sequence, it separates from the DNA

28. Making mRNA • RNA polymerase : enzyme that unravels a segment of DNA (gene) and builds a complementary mRNA strand based off DNA template • Example: • DNA strand: A T G G G A A C T T A C • mRNA strand: U A C C C U U G A A T G • After mRNA strand is complete – DNA reforms and mRNA leaves the nucleus and heads to ribosomes

29. mRNA synthesis animations • Honors biology – transcription animation • Advanced Honors – transcription animation

30. Bacon – summarize the process of transcription for eggs

31. Transcription vs. Replication • The main difference: • Transcription results in one single-stranded mRNA molecule. • Replication results in two double-stranded DNA molecules. Practice • DNA template • DNA Complement (replication) • mRNA (transcription) ATTCGGAGC TAAGCCTCG UAAGCCUCG

32. Eggs – explain how to tell the difference between replication and transcription

33. Stop here and practice!!

34. Bell Work • DNA contains the hereditary information for life. Which structure in DNA illustrates where that information is held? B A C D

35. Bell Work • Pick up your answer sheet for today’s quiz

36. Objectives over next few lessons: • Can differentiate between DNA and RNA • Can explain steps of Transcription • Can explain steps of Translation • Can summarize how to get from DNA code to the expression of a trait • Can summarize the relationship between chromosomes, genes and DNA

37. Face Partners

38. Protein Synthesis – part II • What happens after we transcribe the DNA from the nucleus into the form of mRNA? • We have to “translate” the code on mRNA into a protein

39. Protein Synthesis Animation • Protein Synthesis Overview Animation • Amoeba Sisters – protein synthesis • Teacher’s pet – protein synthesis

40. After we transcribe the message so it can leave the nucleus, we then must have a way to “read” the message.

41. The Genetic Code – what does it code for? • Proteins (polypeptides) - long chains of amino acids that are joined together by peptide bonds. • There are 20different amino acids. • The (sequence) of the amino acids determines the shape of the protein • The shape of a protein determines the function

42. Ross – explain to Rachel the relationship between amino acids and protein function

43. The Genetic Code The genetic code is read 3 letters at a time. A codonconsists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide (protein). The four bases (letters) of mRNA (A, U, G, and C) are read three letters at a time (and translated) to determine the order in which amino acids are added to a protein.

44. The Codon Wheel • 64 different mRNA codons are possible in the genetic code.

45. More than one codon can code for the same amino acid • Example: GGG, GGU, GGA, GGC = Glycine • Some codons give instructions • Example: AUG = start • Example: UGA, UAA, UAG = Stop

46. Cracking the Secret Code • To decode a codon: • start at the middle of the circle and move outward. • Ex: CGA = Arginine • Ex: GAU = Aspartic Acid

47. Rachel – show Ross how to decode the codon GCA

48. Translation Translation takes place on ribosomes, in the cytoplasm or attached to the ER. • rRNA and tRNA will decodethe message on the mRNA strand to produce a polypeptide chain (protein).

49. Rachel – explain to Ross the overall purpose of Translation

50. Translation animation • Virtual Cell – translation animation • Advanced honors – translation • Honors – translation