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
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:
DNA
RNA
Structure
Double Stranded
Single Stranded
Bases- Purines
Adenine (A)
Guanine (G)
Bases - Pyrimidines
Cytosine (C)
Thymine (T)
Uracil (U)
Sugar
Deoxyribose
Ribose
RNA’s JOB = Use DNA code to make proteins!!

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

17. Types of RNA
mRNA – Messenger RNA
rRNA – Ribosomal RNA
tRNA – Transfer RNA
Short single strand that carries a copy of the DNA code for one gene from the nucleus to the ribosome
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. Transcription Nucleus Adenine (DNA and RNA) Cytosine (DNA and RNA)
RNA polymerase
Adenine (DNA and RNA)
Cytosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
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 20 different 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 codon consists 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
rRNA and tRNA will decode the message on the mRNA strand to produce a polypeptide chain (protein).
Translation takes place on ribosomes, in the cytoplasm or attached to the ER.

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

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

51. Messenger RNA (mRNA)
The mRNA that was transcribed from DNA during transcription, leaves the cell’s nucleus and enters the cytoplasm.

52. Transfer RNA (tRNA)
Transfer RNA (tRNA) molecules in the cytoplasm will bond with a specific amino acid
Then, tRNA carries that amino acid to the ribosome
Each tRNA molecule has three unpaired bases called an anticodon.
These bases are complementary to one codon on the mRNA strand.

53. Translation

54. Initiation
Begins when an mRNA in the cytoplasm attaches to the ribosome.
AUG = the start codon
AUG = methionine

55. The Polypeptide “Assembly Line”
tRNA anticodon will temporarily bind to the complementary codon on the mRNA molecule in the ribosome. (This binding of codon to anticodon ensures the correct amino acid is being added)

56. Ross – Tell Rachel how the ribosome knows where to begin “translating” the mRNA strand

57. Elongation
The ribosome has two binding sites, allowing two tRNA molecules to line up, side by side
The ribosome forms a peptide bond between the first and second amino acids on those tRNA molecules
At the same time, the ribosome breaks the bond that held the first tRNA molecule to its amino acid and releases the tRNA molecule.

58. The Polypeptide “Assembly Line”
The tRNA floats away, allowing the ribosome to move down the mRNA molecule and bind another tRNA.
The ribosome continues to move along the mRNA, attaching new tRNA molecules and adding more amino acids to the polypeptide chain.

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

60. Rachel – explain the “assembly line” process of translation to Ross

61. Termination
The process continues until the ribosome reaches one of the three stop codons on the mRNA. Then, the ribosome detaches from the mRNA. The result is a polypeptide (protein chain) that is ready for use in the cell.

62. Practice TAC GGT CCA AAC ACT AUG CCA GGU UUG UGA
DNA template
mRNA (transcription)
Amino Acid Sequence
(translation)
TAC GGT CCA AAC ACT
AUG CCA GGU UUG UGA
Met – Pro – Gly – Leu - Stop

63. Ross – summarize the process of translation for Rachel

64. Translation only animation
– includes the E, P and A site of ribosomes

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

66. All organisms use the same genetic code (A,T,C,G).
This provides evidence that all life on Earth evolved from a common origin.

67. Your Task
Draw a flow chart to show how to get from: