1. Replication, Transcription, and Translation
DNA and RNA
Replication, Transcription, and Translation

2. Genetic Controversy Two schools of thought
a. Some said protein was material
b. Some said DNA was material
How was the controversy settled?
- The scientific experiments of Griffith, Avery, Hershey and Chase

3. Griffith and Transformation
England
- Trying to develop a
vaccine against
pneumonia causing
bacteria
- Two strains - S(smooth)
and R(rough)

4. Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Control (no growth)
Harmless bacteria (rough colonies)
Disease-causing bacteria (smooth colonies)
Heat-killed, disease-causing bacteria (smooth colonies)
Dies of pneumonia
Lives
Dies of pneumonia
Lives
Live, disease-causing bacteria (smooth colonies)

5. RESULTS - Showed that heat killed S strain
and live R strain would kill mice
- Something was “transforming”
the R strain to an S strain
- Called it transformation
- What was the material?

6. Oswald Avery
- Wanted to identify Griffith’s transforming material
- Used two enzymes
a. protein killing
b. DNA killing
- Showed that no transforming took place when DNA “killed”

7. D. Hershey and Chase - 1952 - Working with a bacteriophage
- Virus that infects bacteria
- Made of only two things
a. protein coat
b. DNA (genetic) core

9. Hershey and Chase Phage infects bacterium
Bacteriophage with phosphorus-32 in DNA
Radioactivity inside bacterium
Phage infects bacterium
No radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat

10. Recap: Was DNA or protein injected?
- DNA has phosphorus
- Protein has sulfur
- Used radioactive phosphorus 32P and radioactive sulfur 35S
- Let virus infect bacteria
- New viruses full of 32P
DNA was being injected!

12. The Components and Structure of DNA
1. Called deoxyribonucleic acid
2. Long and thread-like (twisted)
3. Many subunits linked together
4. Subunits called nucleotides
’s in a chain-like structure

13. The structure of a nucleotide
1. Phosphate group - same in all
2. Five carbon sugar
a. deoxyribose sugar
3. Nitrogenous base - 4 different
ones that name the nucleotide

14. Nitrogenous Bases 1. Are different in each nucleotide
2. Names of the four bases
a. adenine (A)
b. guanine (G)
c. thymine (T)
d. cytosine (C)
Two classes of bases
A. purines
1) large double
ring
2) A & G
B. pyrimidines
1) small single
2) T & C

15. Purine and Pyrimidine Structure

16. H. Chargaff
- Studying the amounts of bases in DNA of living things
- His results showed that:
a. A always = T
b. C always = G
- Called Chargaff’s rule
- Also called the base pair rule

17. The molecule is completed…
- Franklin and her X-ray
diffraction picture showed
a helix
Watson and Crick adds
that it is a double helix
with bases in the middle
- Called it a “spiral
staircase”
- Strands are complements of each other
- Think of a step ladder
a. “sides” are alternating
sugar and phosphate
groups
b. “rungs” are base pairs
1) A = T
2) C = G

18. Sugar-phosphate backbone
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Adenine
Thymine
Cytosine
Guanine

19. Chromosomes and DNA Replication
A. DNA Can Make Copies of Itself
1. Process called replication
2. Done during S phase
3. Needed for new cells
4. DNA unwound using helicases
5. Hydrogen bonds broken between bases
6. DNA polymerase puts new nucleotides in place (A to T and C with G)
7. New copy just like original

20. From Genes To Proteins RNA DNA Single-stranded Double-stranded Ribose
Uracil
3 forms of RNA
mRNA (messenger)
tRNA (transfer)
rRNA (ribosomal)
DNA
Double-stranded
Deoxyribose
Thymine

21. From Genes To Proteins…
1. Transcription:
making mRNA
from DNA to
carry information
to the ribosomes.

22. - ALL organisms have a genetic code made of three nucleotide sequences called codons.
- Codons correspond to particular AA and stop signals.

23. From Genes To Proteins…
2. Translation:
Using tRNA to build
proteins from the
information in
mRNA.
- Each tRNA molecule carries an amino acid to the ribosomes, by matching its anticodon to a specific codon from the mRNA

24. GENETIC MUTATIONS Mutations (gene or chromosomal) Changes in DNA
Effect depends on where mutation occurs (body or sex cell) & what type of mutation
Can be helpful, harmful, or neutral

25. Different Types of Gene Mutations
Substitutions = UGU to UGC
Effect depends on translation
Insertions = nucleotides added
Deletions = nucleotides deleted
Transposons= DNA segments move spontaneously from one location to another in the same DNA molecule

26. Ex.
THE CAT ATE THE RAT
(meaningful)
Deletion of C =
THE ATA TET HER AT
(meaningless)

27. Types of Chromosomal Mutations
Deletions (whole or part deleted)
Duplications (extra copies of parts)
Inversions (reverses parts of chromosomes)
Translocations (parts break off and relocate) 27

28. Causes of Mutations? Spontaneous Mutagens (come from environment)
UV light
Chemicals
Carcinogens (cancer causing)

29. RNA (ribonucleic acid)
3 forms of RNA
mRNA (messenger)
tRNA (transfer)
rRNA (ribosomal)
RNA is used to take the information in DNA and make proteins (gene expression)
2 stages of gene expression
Transcription
Translation

30. The Big Idea…
During gene expression, the info in DNA is first transcribed as mRNA and then translated via tRNA and used to build a protein.

31. The Genetic Code

32. The Genetic Code