1. CHAPTER 12 Goal: Understand the purpose of our DNA
CHAPTER 12 Goal: Understand the purpose of our DNA. DNA contains the codes that make proteins. These protein are what we are made of and are necessary for life.
SKIM READ CH 12.1 on pg

2. CHAPTER 12 Goal: Understand the purpose of our DNA
CHAPTER 12 Goal: Understand the purpose of our DNA. DNA contains the codes that make proteins. These protein are what we are made of and are necessary for like.
DNA: THE GENETIC MATERIAL
IT took from 1866 to 1928 for scientists to determine if proteins or nucleic acid (DNA) stored out genetic information

3. Ask your neighbor……where is your DNA located?
Ask your neighbor whether they know if DNA is made of proteins or nucleic acids?

4. Fredrick Griffin- In 1928, he was trying to find a better way to fight pneumonia.
Smooth bacteria injected into mice caused pneumonia! Pg 327 (Figure A)
Rough Bacteria injected into the mice DID NOT cause pneumonia!! (Figure B)

5. If you heat-killed smooth bacteria and injected them into the mice the mice would NOT get pneumonia (Figure C)
If you heat-killed smooth & injected it with live rough bacteria the mice would get pneumonia!!
Griffin took cultures of these mice and when he tested it he found live smooth bacteria!? (Figure D)

6. Griffith’s Experiment: was the 1st major experiment
D: The Rough strain received from the Smooth strain -the disease causing information when they were mixed together

7. Griffin realized that some molecule or group of molecules had changed the harmless rough bacteria in to the harmful smooth bacteria.
BUT he did not know what was causing this change………………..so he named this change -- Transformation

8. OSWALD AVERY- In 1944, reasoned out that genes are what cause transformation.
Avery looked at Griffin’s experiment and set up one where he treated heat-killed bacteria with enzymes that destroyed proteins, lipids, carbohydrates and other molecules.
This DID NOT affect TRANSFORMATION.
He then destroyed the molecule called DNA, and transformation was BLOCKED.
He concluded that genes are made of DNA (DNA- is Deoxyribonucleic Acid)

9. HERSHEY- CHASE- In 1952, Alfred Hershey and Martha Chase set up an experiment to prove that DNA is the transforming factor.
Although many scientist agreed with Avery’s previous conclusion proof was needed.
A BACTERIOPHAGE (or phage) is a virus that affects bacteria. When it affects a bacteria, it replicates (reproduces) within the host.
Phages contain both protein and DNA.
Viruses are not able to replicate on their own.
Hershey and Chase did not know if the protein enters into the host bacteria OR the DNA. Knowing this would tell them what molecules make up the genes of the phage.

10. In their experiment they used Radioactive Isotopes to “mark” what was injected into the bacteria by the virus.
Radioactive isotopes – release small amts. of energy (radioactivity) that can be traced using lab. equipment.
Isotopes are the same element with the same number of protons and electron BUT a different number of neutron in the elements nucleus.
Phosphorus-32 is a radioactive isotope of Phosphorus. Phosphorus is part of DNA, but it is NOT part of proteins, so the phosphorus labels the phage’s DNA.
Sulfur-35 is a radioactive isotope of Sulfur
Sulfur is part of proteins, but it is NOT part of DNA, so the sulfur labels the phage’s proteins.

11. They prepared two samples of bacteria each injected with the different radioactive isotopes
Bacteria infected with the phages with the phosphorus-32 showed radioactivity!
 Bacteria infected with the phages with the sulfur-35 did not show radioactivity.
The genetic material of a bacteriophage was proven to be DNA not proteins.

12. DNA STRUCTURE
P.A. Levene -determined that DNA is made up of the subunits called Nucleotides
Nucleotides are made of:
Backbone structure carbon sugar
2. Phosphate group
Rung structures Nitrogen base
There are 4 types of nitrogen bases:
1. Adenine 2. Thymine
3. Guanine 4. cytosine
These nitrogen bases pair up to form the ladder structure of the DNA molecule.
These nitrogen bases bond together with HYDROGEN bonds
Adenine pairs with Thymine A & T
Cytosine pairs with Guanine C & G

13. DNA STRAND: A- T- G-C- A- G – A- T- G 
Complementary DNA strand:
The orientation of the two strands is also unique: they run antiparallel (tip of pencil to eraser of the other pencil)

14. CHARGAFF’S RULES: When this Biochemist studied DNA he found that there were equal amounts of A & T and of G & C. This shows that Adenine pairs with Thymine and Cytosine pairs with Guanine
Chargaff’s rule:
C = G and T = A

15. ROSALIND FRANKLIN- In 1951 she was studying DNA with a X-ray
ROSALIND FRANKLIN- In 1951 she was studying DNA with a X-ray. Franklin was the first one to image DNA, which caught the attention of Watson and Crick.
The X-ray image did not reveal the structure of the DNA molecule.

16. WATSON & CRICK- In 1953, James Watson and Francis Crick looked at Franklin’s X-ray image and were able to piece together the DNA model.
THE DOUBLE HELIX- two DNA strands twisted around each other, held together with their complementary nitrogen bases bonded together
(DNA MODEL -page 332 in your text)

17. DNA

18. Chromosomes
Average length of a human chromosome is 51 to 245 million base pairs
If a 140 million base pairs were laid out it would be 5 cms long……..
Chromosomes are found in the nucleus of a cell…..all of which are microscopic
HISTONES are what the DNA coils around to form NUCLEOSOMES
Nucleosomes then form CHROMATIN FIBERS that supercoil to form CHROMOSOMES

19. If you were to unwind all of the DNA inside of a cell it would be about 6 ft. long!

20. SECTION CH. 12.2
Goal: To understand the process of DNA Replication- how the DNA makes a copy of itself.
Hmmm….. Who knows what phase of the cell cycle does DNA make a copy of itself??????

21. Chapter 12-2
SEMICONSERVATIVE REPLICATION: This is the process in which the DNA molecule makes a copy of itself.
1. DNA unwinds
2. Both strands serve as a template
3. New stands are produced (One side is original parental DNA and the other is new DNA)
this occurs
in the
S- phase
(synthesis
phase) of the
cell cycle

22. SEMICONSERVATIVE REPLICATION-
In DNA replication, enzymes separate the 2 stands
1. DNA Helicase- unwinds and unzips the DNA strand
2. RNA primase- adds a short segment of RNA called a RNA primer to each strand
DNA is then synthesize using the enzyme DNA polymerase, that adds the appropriate DNA base pair (A, T ,G, or C).

23. One strand is called the leading strand and is elongated as the DNA unwinds
The other strand of DNA, called the lagging strand, elongates away from the replication fork.
The lagging strand is synthesized discontinuously into small segments, called Okazaki fragments

24. Joining the two strands together
DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.
Then the enzyme DNA ligase links the two sections.
Comparing DNA Replication in Eukaryotes and Prokaryotes
*Eukaryotic DNA unwinds in multiple areas as DNA is replicated
*In prokaryotes, the circular DNA strand is opened at one origin of replication.

25. SECTION 12.3
GOAL: TO UNDERSTAND THE PROCESS OF MAKING PROTEINS FROM THE DNA CODE.
SKIM READ SECTION 12.3 PG

26. Protein Synthesis……………

27. Section 12-3 DNA, RNA & Protein
DNA carries the instructions to make the proteins that are needed to create cells and the enzymes needed for all bio-chemical reactions that occur in all living organisms.
Central Dogma (or Central Idea/ belief):
DNA codes for RNA which guides protein synthesis (or the making of proteins)

28. Protein Synthesis (pg. 336-339): creating proteins from the DNA code
Two steps:
1. Transcription 2. Translation
Involves:
1. DNA
2. mRNA (messenger RNA)
3. rRNA (ribosomal RNA)
4. tRNA (transfer RNA)
RNA background info.: 1. RNA’s 5-carbon sugar is ribose 2. it is usually single stranded 3. Uracil (U) pairs with Adenine (A). It does not contain Thymine (T)

29. STEP 1. Transcription
This is the process of making mRNA from the DNA sequence.
Occurs in the nucleus of the cell because DNA does not ever leave the nucleus.
RNA polymerase is the enzyme that unwinds and unzips the DNA strand to make mRNA
Once the mRNA is constructed from DNA it can leave the nucleus and travel out into the cytoplasm of the cell to the rRNA.
rRNA are ribosomes

30. Transcription: Occurs in Nucleus of cell

31. When the mRNA is made from the DNA sequence some of the DNA instructions are not put into the mRNA intentionally.
These left out sequences are called INTRONS (or intervening sequences)
The DNA codes that are put into the RNA are called EXONS

32. mRNA leaves the nucleus and heads for a ribosome (rRNA) located in the cytoplasm where step 2 can occur……
STEP 2. Translation: is when the mRNA code is translated by tRNA to make proteins The mRNA is read 3 base pairs at a time. These 3 base pairs are called CODONS

33. The tRNA also carries 3 base pairs that are called ANTICODONS.
The mRNA moves through the rRNA (ribosome) as it does this the tRNA matches it anticodon with the mRNA’s codon.

34. The tRNA is a folded RNA cloverleaf shaped strand that has a specific amino acid attached to it (based on it anticodon base pairs)
Proteins are made of amino acids linked together
The tRNA brings the correct amino acid to the mRNA and releases the amino acid which links them together creating a protein.
The tRNA then goes and gets more of it specific amino acid and continues to create more proteins

35. 1. DNA transcription: DNA to mRNA 2
1. DNA transcription: DNA to mRNA 2. Translation: mRNA moves through rRNA in cells cytoplasm. tRNA brings amino acids in proper sequence creating Proteins

36. http://www. youtube. com/watch

37. 12.4 Eukaryotic Gene Regulation
Controlling Transcription: Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amounts
Activators
Repressors

38. Prokaryote Gene Regulation:
The ability of an organism to control which genes are transcribed in response to the environment.
An operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway

39. HOX Genes
Hox genes are responsible for the general body pattern of most animals.

40. Mutations
Types of mutations:
1. Point mutations: involve a chemical change in just 1 base pair
2. Insertion: A nucleotide is added to the sequence
3. Deletion: A nucleotide is removed from the sequence
A permanent change that occurs in a cell’s DNA is called a mutation