1. DNA
Chapter 12

2. DNA Holds our genetic information Like a library
Important for mitosis to occur
Biologists had to discover the chemical nature of DNA to determine that it is responsible for our genetic information

3. Griffith and Transformation
Transformation: when a strain of bacteria is changed by a gene or genes from another bacteria
Experiment
Inject mice with bacteria containing virus for pneumonia
Smooth colonies = have bacterial infection
Rough colonies = harmless bacteria

4. Griffith and Transformation
If the virulent colonies were killed with heat and mixed with harmless bacteria, then the harmless bacteria get transformed into virulent bacteria
Some factor of the bacteria was transformed to harmless bacteria

5. Avery and DNA Wanted to repeat Griffith’s experiment
Treated heat-killed virulent bacteria with enzymes
One enzyme destroyed RNA and proteins
Another enzyme destroyed ONLY DNA
Lethal Virus

6. Avery and DNA
Lethal Virus
Results showed that bacteria treated with DNA destroying enzyme did not transform harmless bacteria into virulent bacteria
It is the DNA that stores the genetic information from one generation to the next
Lethal Lethal Non Lethal

7. Hershey-Chase Bacteriophage: a virus that infects bacteria ONLY
Scientists wanted to see what gets injected into a bacteria to cause infection
Used a radioactive marker for DNA and protein

8. Hershey Chase
After infection, the bacteria that had radioactive marker on DNA showed that it is the DNA that is inserted into the bacteria
Results: DNA from the virus is what causes infection
Hershey-Chase Experiment

9. DNA Structure Monomer of DNA is a nucleotide
5-carbon sugar
Phosphorous group
Nitrogenous base
4 Nitrogenous bases in DNA
Adenine
Guanine
Thymine
Cytosine

10. DNA Structure Backbone of DNA is the sugar and phosphate
Nitrogenous bases stick out of side to form ladder rungs
These bases are repeated in a pattern that form our genetic code

11. DNA Structure Chargaff’s Rule
Scientist that discovered a pattern between the 4 bases
Same percentage of Adenine as Thymine
Same percentage of Guanine as Cytosine
Scientists still not sure how they match up though

12. DNA Structure Rosalind Franklin
Scientist that worked with X-ray diffraction
Used X-rays on a portion of DNA and the results showed an X pattern

13. DNA Structure Watson & Crick
Scientists that were able to understand Rosalind’s X-ray picture
Result: DNA has a double helix pattern where the nitrogenous bases face each other

14. DNA Structure DNA has a double helix pattern
Looks like a ladder twisted up
The sides of the ladder are the sugar and phosphate and the rungs of the ladder are the nitrogenous bases paired up
The adenine binds to thymine
The guanine binds to cytosine
This concluded Chargaffs’s rule  base pairing

15. DNA and Chromosomes Prokaryotes Eukaryotes Lack nucleus and organelles
DNA floats as a circle in the cytoplasm
Eukaryotes
1000 times more DNA than prokaryotes
DNA is located in nucleus
Specific number of chromosomes
Ex: Humans have 46 chromosomes

16. DNA and Chromosomes DNA Length Chromosome Structure DNA is very long
DNA is coiled up into a very small space because it is in chromatin form
Chromosome Structure
Tightly packed chromatin is wrapped around small proteins called histones
When chromatin gets super coiled you create a chromosome

17. DNA Replication
Each strand of DNA is needed to be a template for a new strand of DNA to be produced
Since you can use one strand to make the other side, they are said to be complementary

18. Duplicating DNA
Before mitosis occurs, DNA needs to be duplicated first during interphase
When DNA duplicates, its called replication
DNA molecules separates into two strands, then produces two new complementary strands following the rules of base pairing
Each strand serves as a template for the new strand

19. How Replication Occurs
Enzymes help make new strands of DNA
One enzyme called helicase “unzips” the DNA, separating the base pairs
DNA polymerase adds new bases to pair up with the template
This enzyme also proofreads to make sure everything matches
What would be the matching bases to the part of DNA shown below?

20. RNA & Protein Synthesis
Sections 3-4
RNA & Protein Synthesis

21. Structure of RNA Made of nucleotides
Three differences between DNA & RNA
Sugar
DNA = deoxyribose sugar
RNA = ribose sugar
RNA is single stranded
RNA uses Uracil instead of Thymine to bond with Adenine

22. Types of RNA Three types of RNA mRNA rRNA tRNA Messenger RNA
Ribosomal RNA
tRNA
Transfer RNA

23. Types of RNA Messenger RNA
This is a copy of complimentary strand of DNA
Eventually will code for a protein to be made

24. Types of RNA Ribosomal RNA
RNA found in ribosomes (organelles in the cell)
Ribosomes are the factory for protein synthesis

25. Types of RNA Transfer RNA Help produce a protein from mRNA
Brings amino acids (monomer of protein) to ribosome to bond them together and make a whole protein

26. Transcription Taking DNA and making an RNA copy
Occurs in the cell’s nucleus
RNA polymerase opens the DNA and adds RNA copy to the template
Once this is made it is called pre-mRNA

27. RNA Editing Pre-mRNA is a rough draft to the final copy of mRNA
Some parts of pre-mRNA are not needed to make a protein
These unnecessary parts are called introns
Introns get cut out of pre-mRNA
Before leaving the nucleus, mRNA needs to get a cap and tail to finalize the RNA strand

28. The Genetic Code Proteins are made of 20 possible amino acids
In order to make a protein from a strand of mRNA, the mRNA is read in a 3 letter sequence called codons

29. The Genetic Code Each three letter codon represents an amino acid
DNA = AGCGTGCCA
RNA =
Codons =
Amino acids =

30. The Genetic Code Each three letter codon represents an amino acid
DNA = TACCGTCCGGTCATC
RNA =
Codons =
Amino acids =
DNA = AGCGTGCCAATT

32. The Genetic Code
RNA knows when to start and stop based on the codons read
There is ONE start codon: AUG
There are THREE stop codons: UAA, UAG, UGA

33. Translation Taking mRNA and making a protein
Occurs in the cytoplasm on a ribosome
tRNA brings specific amino acids to ribosome
If mRNA = AUG, then tRNA = UAC
The tRNA has the anti-codon

34. Translation
As new tRNA brings amino acids to the ribosome, past ones break off leaving just amino acids bonded to each other
This continues until one of the three STOP codons is met
Finished amino acid strand goes through protein folding

35. Mutations Changes in the DNA sequence that affect the cell
Two types of mutations
Gene mutation
Chromosomal mutation

36. Gene Mutation Point mutation Frameshift mutation
A change in one nucleotide in a DNA sequence
Occur only in a single point of the DNA
Can sometimes be a problem
Frameshift mutation
A change in the reading frame of DNA
Since DNA is read in 3 letter codons, if there is an insertion, deletion, or large change in these codons the frame is changed

37. Chromosomal Mutation A change in the number of chrom0somes in the cell
Four types
Deletion
Duplication
Inversion
Translocation