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. 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

10. 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

11. 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!!

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

13. 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.

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

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

16. DNA Structure
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

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

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

19. DNA cannot leave the nucleus, so…

20. DNA
GENE
RNA
Ribosome
Protein
Trait

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

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 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 What is the ultimate purpose of the genetic code in DNA?
How do we “read” that code?

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

36. PROTEIN SYNTHESIS STANDARDS OBJECTIVES
CLE Investigate how genetic information is encoded in nucleic acids.
CLE Describe the relationships among genes, chromosomes, proteins, and hereditary traits.
Use models of DNA, RNA, and amino acids to explain replication and protein synthesis.
Investigate how the genetic code carried on mRNA is translated into a protein
Practice “decoding” genetic codes
Create unique genetic code to encrypt a secret message

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

38. The Genetic Code
The “language” of mRNA instructions is called the genetic code.
This code is written in a language that has only four “letters” (A,G,C,U)
How can a code with just 4 letters carry instructions for 20 different amino acids?

39. The Genetic Code – what does it code for?
Proteins (polypeptides) - long chains of amino acids that are joined together.
There are 20 different amino acids.
The structure and function of proteins are determined by the order (sequence) of the amino acids

40. 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.

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

42. 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

43. 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

44. Cracking the Code
This picture shows the amino acid to which each of the 64 possible codons corresponds.
To decode a codon, start at the middle of the circle and move outward.
Ex: CGA
Arginine
Ex: GAU
Aspartic Acid

45. 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.

46. Translation animation Translation animation – mcgraw hill

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

48. 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.

49. tRNA molecule
Anticodon

50. Translation

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

52. 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)

53. 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.

54. 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.

55. 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.

56. Practice TAC GGT CCA AAC ACT AUG/CCA/GGU/UUG/UGA UAC/GGU/CCA/AAC/ACU
DNA template
mRNA (transcription)
tRNA
Amino Acid Sequence
(translation)
TAC GGT CCA AAC ACT
AUG/CCA/GGU/UUG/UGA
UAC/GGU/CCA/AAC/ACU
Met-Pro-Gly-Leu-Stop

57. Computer Practice for transcription and translation

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

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