1. DNA and RNA
Ch. 12 and 13

2. Griffith’s Experiments
They were done to determine whether genes are made up of DNA or protein.
He injected bacteria into mice in four separate experiments.

3. His results.. Streptococcus pneumonia bacteria were used.
S bacteria caused pneumonia and death when injected.
R bacteria had no visible effect.
Heat killed S bacteria did no harm.
Heat killed S and live R were injected and the mouse died of pneumonia.
Streptococcus pneumonia bacteria were used.
S strain was smooth and caused pneumonia.
R strain was rough and did no harm.

5. What can we conclude? What was this transforming material? DNA
If the mice died with S and heat-killed S and R, but not when S was heat-killed or R by itself, then there had to be some transforming material that was transformed from the heat-killed S to living R changing it into S bacteria.
What was this transforming material?
DNA

6. Oswald Avery Repeated Griffith’s experiment.
Discovered that it is the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.

7. Hershey and Chase’s Experiment
2 experiments.
Used bacteriophages (viruses) that injected radioactive material into bacteria. They they looked to see if the bacteria became radioactive.
Phages with green radioactive DNA 32-P injected it into bacteria and the bacteria became radioactive.
Phages with green radioactive protein 35-S injected it into bacteria and it did not become radioactive.
What can we conclude?

9. DNA Structure Deoxyribonucleic acid
Double Helix
5’C sugar, Deoxyribose
Phosphate Group
4 Nitrogen Bases
First double helix structure built by Watson and Crick
Published in 1953
Remember that the structure of a molecule is related to its function, so knowing what a molecule looks like gives researchers insight into how DNA works.
What do you know about DNA?
Nucleotide

11. Purines and Pyrimidines make up the 4 N bases
Purines- larger
Adenine and Guanine
Pyrimindines- smaller
Cytosine and Thymine
Pairing of the bases in the DNA structure: Chargaff’s Rule
(amount of A = amount of T and amount of C =amount of G
A—T
C—G

12. Discovery of DNA: X-Ray evidence
Rosalind Franklin used X-ray diffraction to reveal the shape of DNA.
The X-shaped pattern shows that the strands of DNA are twisted around each other.

13. Double Helix The shape of DNA is that of a “twisted ladder”.
The P group is attached to the sugar and that forms the backbone.
The “rungs” of the DNA are the pairing of the bases.
Watson and Crick

14. DNA Replication Semi-conservative
The DNA unzips. Enzymes split apart the base pairs and unwind the DNA.
Free nucleotides in the cell find bases to pair up with on each side along the “open” DNA via DNA polymerase.
The sugar-phosphate backbone completes the 2 new DNA strands.
Each strand has a new and old strand.
DNA Replication Simulation

15. In depth DNA Replication
1. Antiparallel strands. Replication is 5’ to 3’
2.Topoisomerase (DNA gyrase) relieves superhelicity downstream of replication fork.
3. Helicase unwinds ds DNA.
4. Primase synthesizes the RNA primers for lagging strand, complexes with helicase. (not shown)
5. Ssb proteins keep DNA from reannealing.
6. DNA pol III polymerizes leading and lagging strand.
7. Lagging strand- okasaki fragments
8. DNA pol I- removes RNA primers and replaces with DNA.
9. DNA ligase seals gaps

17. Cloning
Clone the Mouse
A clone is a member of a population of genetically identical cells produced from a single cell.
In 1997, Dolly the sheep was the first clone of an adult mammal. It took over 500 tries.

18. Human Cloning?
Why or Why not?

19. Protein Synthesis
Process when the organism’s genotype is translated into it’s phenotype.
Remember that proteins are made up of chains of Amino Acids.
How many a.a. are there?
2 Processes
Transcription- DNA to RNA
Translation- RNA Protein
1.26 The genetic material in DNA molecules provides the instructions for assembling proteins. This works the same in nearly all life forms.

20. DNA vs. RNA DNA Double Stranded Base Pairs (A-T, G-C)
Deoxyribose sugar
RNA
Single Stranded
Base Pairs (A-U, G-C) Uracil is used instead of Tymine
Ribose Sugar

22. Transcription RNA polymerase unwinds a section of DNA
RNA polymerase binds unattached RNA nucleotides to complementary DNA strand at promoter region.
A new strand of mRNA (messenger RNA) is made.
DNA will signal RNA pol to leave and transcription stops.
It occurs in the nucleus.
Tutorial

23. RNA splicing Before mRNA can leave the nucleus, RNA must be spliced.
It gets rid of introns and exons are spliced together.
mRNA now leaves the nucleus and into the cytoplasm where it finds a ribosome.
Introns- non-coding regions of DNA or RNA.
Exons-coding regions

24. Things to Know before we go on.
Codon- 3 base sequence of mRNA that codes for an amino acid.
Anti-codon: complementary 3 base sequence to mRNA on a tRNA.
rRNA- ribosome where amino acids are put together.
tRNA (transfer RNA)- matches up anticodons to codons to make amino acids that form proteins.

26. Translation
3. A 2nd tRNA brings in the next one and then a peptide bond bonds the 2 a.a. together. It moves over and the 1st one leaves so the next one can come in.
rRNA attaches to first codon on mRNA.
A tRNA brings an a.a. to the rRNA with the anti-codon and matches it up with the codon.

27. Starting and Stopping Translation
AUG- Methionine is the Start Codon.
There are 3 Stop Codons: UAA, UAG, and UGA.

29. Protein synthesis

30. Frameshift mutations (Gene mutation)
When nucleotides are deleted or added, it changes the order or code of the codons, results in different a.a.

31. Point Mutations (Gene mutation)
Occur when there is only one change in the nucleotide. It only changes one a.a. coded for.

32. Jumping Genes (Transposons)
Occurs when a large stretch of DNA is inserted into the gene.
Multicolored corn
1.28b Genetic variation occurs from crossing over, jumping genes and deletion and duplication of genes.

33. Polyploidy When nondisjuction occurs in all chromosome pairs.
Occurs often in plants and can make them “robust”.

34. Control over Genes
Ch. 14

35. Control Over Genes
Regulatory proteins intervene before, during or after gene transcription or translation. Ie. Hormones, initiate changes in cell activities when they dock at suitable receptors.
Negative control- slow or stop gene action
Positive control- promote or enhance it

36. Promoters and Enhancers
Promotors- noncoding sequence that marks where to start transcription.
Enhancers- binding sites for activator proteins.

37. Structure Determines Function
When genes are changed, the proteins they code for may change and this can affect cell structure and function,which changes a phenotype.
The control of gene expression (protein synthesis), is different in prokaryotes and eukaryotes.

38. Gene Expression Prokaryotes Eukaryotes
Genes turn on and off primarily in response to changes in environmental factors.
1.1b Different parts of the genetic instructions are used in the different kinds of cells and are influenced by the cell’s environment and past history.
Eukaryotes
Gene regulation involves several complex systems.
Most eukaryotic genes are controlled individually and have regulatory sequences that are much more complex.
TATA box

39. Operons A group of genes that operate together are known as operons.
In E.coli there are 4288 protein encoding genes that are turned off and on together.
Because the genes must be expressed in order for the bacterium to be able to use the sugar lactose as food, they are called lac operon.

40. Gene Regulation in Prokaryotes
The regulatory gene codes for production of the repressor that binds to DNA, preventing RNA pol from binding to the promoter. Protein synthesis can’t occur.
Lac genes (operon)- group of genes that operate together.

41. The repressor is inactivated.
2. Enzymes bind to the repressor and changes it’s shape so it can’t combine to DNA. Now, RNA pol can bind to promoter.

42. The Genes are On
3. RNA pol moves along DNA where mRNA is translated to produce product. When there is enough “product” in the cell, the repressor takes back original shape and turns genes back off.

43. Analogy of Gene Regulation in Prokaryotes
An analogy to gene control would be when a house gets below a certain temp. the furnace kicks on and when it is hot enough it turns back off.
What would the promoter be?

44. Gene Expression in Eukaryotes
TATA box is about 30 bp long and helps RNA polymerase to find position by marking a point just before the point for transcription to begin.

45. Development and Differentiation
Differentiation- cells become specialized in structure and function.
Hox genes- control the differentiation of cells and tissue in the embryo. A mutation can completely change the organs that develop in specific body parts. Legs instead of antennae on fruit fly can grow on head.

46. Hox gene clusters
What do you recognize about where each gene controls in each organism?

47. Knockout genes- knock out gray fur genes
Stem cells
Genetic recombination

48. Add to “white” cells