1. From DNA to Proteins
Ch. 8

2. DNA Genetic Code- program of the cell which relates to heredity
How did scientists learn that the genetic code is DNA?
Frederick Griffith (1928)- discovered transformation- process by which genetic material is absorbed from the environment and incorporated into the bacteria's DNA

3. Griffith’s Experiment-finding the transforming principle
injected mice with noncapsulated bacteria (R)- mice live
injected mice with capsulated bacteria (S)- mice died
injected mice with heat killed capsulated bacteria(S)- mice lived
injected mice with heat-killed capsulated (S) and noncapsulated
bacteria (R)- mice died

4. Griffith’s Experiment

5. Identifying DNA as the transforming principle
Avery, McCarthy and MacLeod (1944)- proved DNA was transforming factor
used protein destroying enzymes and transformation occurred
used DNA destroying enzymes and no transformation occurred

6. Hershey and Chase confirm DNA is genetic material
Hershey and Chase (1952)- studied bacteriophages (viruses which infect bacteria) and proved that DNA was the genetic info.
tagged protein coat of virus with radioactive sulfur
tagged DNA of virus with radioactive phosphorus
introduced virus to bacteria and found that the radioactive P entered the bacteria

7. Hershey and Chase

8. Structure of DNA Composed of nucleotides 5-C sugar (deoxyribose)
phosphate group
nitrogenous base
purines = adenine and guanine
pyrimidines = cytosine and thymine

9. Structure of DNA phosphate group nitrogen-containing base
deoxyribose (sugar)
nitrogen-containing
base

10. Structure of DNA

11. The Base Pair Rule
Chargaff- determined that adenine bonds to thymine and cytosine bonds to guanine
same 4 bases are used by all organisms but in different quantities and order

12. The Base Pair Rule
hydrogen bond
covalent bond

13. The Double Helix
Watson and Crick with the help of Wilkens and Franklin determined that DNA is a double helix
Franklin’s x-ray crystallography work was extremely important
they won the Nobel Prize in 1962 (except for Franklin who died before the award was given)

14. The Double Helix

15. DNA Replication
DNA Replication- process by which DNA makes a copy of itself in order to produce two identical cells
1. DNA is uncoiled with enzymes
2. DNA polymerase- enzyme which then bonds the complementary nucleotides together
3. Each new DNA molecule has one original and one new strand (semiconservative model)

16. DNA unzips in both directions
DNA Replication
DNA unzips in both directions
nucletodies

17. DNA Replication
DNA polymerase
new strand
nucleotide

18. DNA Replication
original strand
new strand
Two molecules of DNA

19. RNA
RNA- nucleic acid which acts as a messenger between DNA and the ribosomes for protein synthesis
Central Dogma- information flows from DNA to RNA

20. Structure of RNA Structure- single stranded 5-Carbon sugar (ribose)
phosphate group
nitrogenous base
purines- adenine and guanine
pyrimidines- cytosine and uracil

21. Transcription
Transcription- process by which information is transferred from DNA to RNA in sets of three nucleotides (codon)
only the part of DNA which has the code for the protein is copied
messenger RNA (mRNA)- copies and carries information out of nucleus to ribosome

22. Transcription
introns are genes not used to make a protein (these get cut out before
mRNA leaves the nucleus), exons are genes used to make a protein

23. Transcription
start site
nucleotides
transcription complex

24. RNA polymerase moves along the DNA
Transcription
DNA
RNA polymerase moves along the DNA

25. Transcription
RNA

26. Translation
Translation- decoding of mRNA in order to form proteins (assisted by transfer RNA- tRNA and ribosomal RNA - rRNA)
tRNA reads in sets of 3 called the anticodon

27. Translation
codon for
methionine (Met)
leucine (Leu)

28. Translation
The genetic code matches each RNA codon with its amino acid or function.

29. Translation
A change in the order in which codons are read changes the resulting protein.

30. Translation Machinery tRNA

31. Translation Machinery Ribosome

32. Translation

33. Translation

34. Translation

35. Mutations Random changes to DNA
Point mutation- one nucleotide is substituted
Frameshift mutation- insertion or deletion of a base resulting in a shift as to how the codon is read
Mutagens- agents which can change the DNA (UV light, industrial chemicals etc.)

36. Mutations
mutated
base

37. Mutations