1. How does DNA instruct cells to make PROTEINS?

2. Part I DNA, Genes, and Proteins

3. DNA and genes Some stretches of DNA are called genes.
Genes are stretches of nucleotide bases (DNA) that code for proteins.
Proteins are used to build cells and do much of the work inside cells.

4. Genes and Proteins
Each gene code is copied in the nucleus and taken to the cytoplasm.
Here the code is deciphered and converted into a string of amino acids (a protein)
Each different protein has its own gene, somewhere on the chromosome, that codes for it.

5. Part II COPYING THE GENE

6. DNA cannot leave the nucleus of eukaryotic cells
DNA cannot leave the nucleus of eukaryotic cells... but proteins are made outside of the nucleus by organelles called ribosomes
human cheek
cell
Elodea leaf cell
mitochondria
chloroplasts
vacuole
nucleus
(DNA here)
(DNA here)

7. Think of ribosomes as factories that make proteins
(proteins made here)
(proteins made here)
nucleus
(DNA here)
(DNA here)

8. DNA and ribosomes are at different locations in a prokaryotic cell.
(proteins made here)
ribosomes
Q. Ribosomes make protein but are not in the same location as DNA in a cell. How can proteins be made according to the DNA information when they are in different places?

9. A. Take a copy of the Gene to the ribosome.
mRNA transfers a copy of the gene on the DNA in the nucleus to the ribosomes.
Ribosomes build proteins according to the mRNA information received.

10. mRNA: the messenger
RNA is how the body gets information from the nucleus (DNA) to the
place where
protein gets made (ribosomes)

11. Information flow from DNA to trait
Observed trait
DNA
protein
Made by ribosomes outside of nucleus
Stored in nucleus

12. Information flow from DNA to trait
messenger
RNA
Observed trait
DNA
protein
Made by ribosomes outside of nucleus
Stored in nucleus

13. DNA information  mRNA information
messenger
RNA
DNA
Transcription is the process used to convert DNA information into mRNA information.
Note: DNA does not become RNA; the information in DNA is copied as RNA

14. Part III RNA (Ribonucleic acid) and Transcription

15. What is RNA, anyways? How is it different than DNA?

16. Differences between DNA and RNA
Double strand
Deoxyribose sugar
Contains thymine
(and A, G, & C)
Very large molecule
RNA
Single strand
Ribose sugar
Contains uracil
(and A, G, & C)
Small molecule

17. Different Sugars DNA RNA Can you spot the difference?
RNA
Can you spot the difference?

18. Different Bases Can you spot the difference?
Can you spot the difference?

19. (double stranded, kept “safe” in nucleus) (single stranded - mobile)
RNA IS COPIED FROM DNA
DNA
(double stranded, kept “safe” in nucleus)
Genes are Copied
RNA
(single stranded - mobile)

20. The Transcription process
Promoters are a specific set of bases on DNA that show where a gene begins.
For transcription to occur, the enzyme RNA polymerase binds to DNA at the promoter and separates the DNA strands
RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into a copy of the gene (mRNA)

21. The Transcription Process
Terminators! Are a specific set of bases to show where the gene ends.
RNA polymerase stops copying the gene here, moves off to find another gene, the transcript is released and the DNA “zips” back up.

22. Transcription of RNA from a template strand of DNA

23. Transcription DNA zips back together DNA unzips DNA ACTTTACGGCAT
ACTTTACGGCAT TGAAATGCCGTA
ACTTTACGGCAT TGAAATGCCGTA
RNA copy made
ACUUUACGGCAU
TGAAATGCCGTA
RNA
ACUUUACGGCAU

24. If the DNA sequence is this:
TACGAGTTACATAAA ATGCTCAATGTATTT
What is the sequence of the mRNA?
(Use the bottom strand as the template for mRNA)
UACGAGUUACAUAAA

25. Animation of Transcription

26. Part IV Decoding the mRNA: What is the code?

27. The Genetic Code “The Problem”
Somehow we need to read the order of nucleotides on mRNA and have that tell us the order of amino acids within each protein
As there are 20 amino acids and only 4 different bases each nucleotide on its own cant specify the position of a different amino acid

28. The genetic code “The solution”
If a word can only be a single letter long how many words can there be in the English language?
If we can have two letters form a word how many words can we make now? (aa, ab, ac, ba, bb, bc, etc.)
If two nucleotides can code for an amino acid how many amino acids can we code for?
There are 64 possible ways to combine three nucleotides (43). More than enough to code for 20 amino acids.

29. The Codon
A codon is a set of three nucleotides on mRNA and designates an amino acid
There are 20 amino acids, but 64 possible codons
So each amino acid may have more than one codon that codes for it.

30. A Codon Chart Decode by reading the first then second then third base.
Example: AUG codes for Methionine

31. Part IV Turning mRNA into protein: Translation

32. Introducing…. Another RNA molecule; the final player in our story…
tRNA

33. Transfer RNA (tRNA)
An RNA molecule with attachment site at one end for an amino acid.
The opposite end has three nucleotide bases called the anticodon.
If there are 64 possible codons how many different tRNA molecules do you think there are?

34. Transfer RNA
Amino acid
amino acid
attachment site U A C
anticodon

35. Codons and Anticodons
Amino Acid
The 3 bases of an anticodon are complementary to the 3 bases of a codon
tRNA
anticodon
UGA
GCAAUCACUACGGCA
codon

36. Translation
Translation is the process of of decoding the mRNA into a protein.
Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins

37. 1. A Ribosome binds to mRNAU G C

38. 2. The Ribosome helps the correct tRNA bind to mRNAG
aa2 A U
1-tRNA U A C
aa1
anticodon A U G C U A C U U C G A
hydrogen
bonds
codon
mRNA

39. The Ribosome then helps the next correct tRNA bind to mRNA and a peptide bond formsG A
aa3
aa1
aa2
peptide bond
1-tRNA
2-tRNA U A C G A U A U G C U A C U U C G A
mRNA

40. Ribosomes move over one codon
aa1
4. All Change !!
3-tRNA G A
aa3
aa2
1-tRNA U A C
(leaves)
2-tRNA G A U A U G C U A C U U C G A
mRNA
Ribosomes move over one codon

41. G C U aa4 aa1 5. Etc. Etc. !! aa2 aa3 G A U G A A A U G C U A C U U C
4-tRNA G C U
aa4
aa1
5. Etc. Etc. !!
aa2
aa3
2-tRNA
3-tRNA G A U G A A A U G C U A C U U C G A A C U
mRNA

42. Ribosomes move over one codon
peptide bonds
4-tRNA G C U
aa4
aa1
aa2
aa3
2-tRNA G A U
(leaves)
3-tRNA G A A A U G C U A C U U C G A A C U
mRNA
Ribosomes move over one codon

43. peptide bonds aa1 aa2 aa4 aa3 G A A G C U G C U A C U U C G A A C U
3-tRNA
4-tRNA G A A G C U G C U A C U U C G A A C U
mRNA

44. Ribosomes move over one codonU G A
5-tRNA
aa5
aa1
aa2
aa3
aa4
3-tRNA G A A
4-tRNA G C U G C U A C U U C G A A C U
mRNA
Ribosomes move over one codon

45. aa5 aa4 aa3 primary structure of a protein aa2 aa1 A C U C A U G U U U
terminator
or stop
codon
200-tRNA A C U C A U G U U U A G
mRNA

46. End Product –The Protein!
The end products of protein synthesis is a primary structure of a protein
A sequence of amino acid bonded together by peptide bonds
aa1
aa2
aa3
aa4
aa5
aa200
aa199

47. A Gene (DNA) A Protein A U G C aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds
mRNA
start
codon
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
codon 1
methionine
glycine
serine
isoleucine
alanine
stop
codon
protein
A Protein
aa1
aa2
aa3
aa4
aa5
aa6
peptide bonds

48. THE END!!!