1. DNA (DEOXYRIBONUCLEIC ACID)

2. The Search for Genetic Material  Up to this point, we know that there are chemical factors called genes that pass traits from one generation to the next  What was unknown though was what were genes made of  Scientists begin to search for the genetic material

3. First Discovery  Fredrick Griffith was a scientist that was interested in bacteria  Specifically what/how bacteria caused disease such as pneumonia  He isolated 2 similar types of pneumonia bacteria from mice and grew them in culture  Smooth Bacteria – caused pneumonia  Rough Bacteria – didn’t cause pneumonia  When Griffith injected the mice with the 2 strains, he saw very different results  Smooth Strain - Mice die  Rough Strain – Mice live  Griffith wanted to know if the disease causing strain was the result of a poison produced by the bacteria

4. More Experimenting  To figure out what exactly was causing the mice to die, he heat killed the disease causing (smooth) bacteria  Mice injected with heat killed smooth bacteria, the mice live  Since the mice are still alive, the initial death was not caused by a poison  Griffith then combines heat killed smooth bacteria and live rough bacteria  Mice injected with this combiniation results in the mouse death  When Griffith removed the bacteria from the dead mice, he saw that they were all filled with the smooth (disease- causing) bacteria  How did this happen?

5. Transforming Principal  Somehow the heat killed strain passed their disease causing abilities to the harmless strain  Griffith called this process transformation  One strain (harmless rough) had been permanently changed into another (a disease causing strain)  The information that caused disease must have transformed the information originally that did not cause disease  Since the ability to cause disease was inherited, it must be caused by a gene

6. Griffith’s Transforming Experiment

7. The Search Continues…  In 1944 Oswald Avery repeated Griffith’s work and tried to determine what the genetic material was  He used the same bacteria (S &R) and injected them with different enzymes 1. First injected with enzymes to destroy molecules such as proteins, carbohydrates, lipids and RNA Transformation still occurs 2. Second, he injects with enzymes to destroy DNA Transformation does not occur  This is the first ground-breaking evidence that shows that DNA is the genetic material  Avery presented this material in 1944 but there was still skepticism…

8. Still wanna know…  Alfred Hershey and Martha Chase studied bacteriophages (phage) viruses that infect bacteria  They phages are made up of a DNA core and protein coat  How does a virus work?  They land on a cell and inject their genetic material into the cell

9. DNA it is!  They placed radioactive markers for 2 different materials on phages and injected them into bacteria 1. First was a sulfur marker If protein was the genetic material injected, there would have been radioactivity inside the bacterium No radioactivity was seen 2. Second was a phosphorus marker If DNA was the genetic material injected, there would have been radioactivity inside the bacterium Radioactivity was detected!  Finally proves that DNA is the genetic material

10. Hershey-Chase Experiment

11. DNA structure  Scientists were happy to know that DNA was the genetic material  They now had new questions 1. How did genes (and therefore DNA) carry genetic information from one generation to the next 2. How was it that DNA created the characteristics of organisms 3. How was it that DNA was copied with each cell division  They knew DNA had to be a very special molecule

12. DNA Structure  DNA is a long molecule made of units called nucleotides  Each nucleotide is made of 3 parts 1. 5 Carbon Sugar – Deoxyribose 2. Phosphate Group 3. Nitrogenous Base (nitrogen containing)  There are 4 different nucleotides that make up DNA and the only difference is the nitrogenous base Forms the backbone Forms the steps to the ladder

13. Nitrogenous Bases  There are 2 groups of nitrogenous bases 1. Purines (have 2 rings) 1. Adenine (A) 2. Guanine (G) 2. Pyrimidines (have 1 ring) 1. Cytosine (C) 2. Thymine (T)

14. Nitrogenous Bases Thymine Cytosine

15. How does DNA do it?  Scientists were baffled to think that 4 different nucleotides were responsible for all of a genes properties  They wondered how these 4 molecules could be strung together to make so many different genetic possibilities

16. Chargaff’s Rules  In 1950 Erwin Chargaff looked at the relationships of the 4 nitrogenous bases in samples of DNA  He saw that percentages of Adenine (A) were always the same as Thymine (T)  He saw that percentages of Cytosine (C) were always the same as Guanine (G)

17. DNA Model  In the early 1950’s Rosalind Franklin used x-rays to try to determine the structure of DNA.  These x-rays showed an x pattern with a circle around it  This image suggested that there were 2 strands with the nitrogenous bases located near the center

18. DNA Model  Franklin’s coworker, Maurice Wilkins showed the data without Franklin’s consent to 2 scientists James Watson and Francis Crick  Watson and Crick were trying to understand and determine the structure of DNA by building a 3-D model  They use Franklin’s finding to support their own data and determine the structure of DNA - The Double Helix  They present this double helix in a published paper in 1953

19. DNA Model  Watson, Crick and Wilkins were awarded the Nobel Prize in 1962 for their discovery

20. DNA Model Continued…  As mentioned before, there are 4 nucleotides  A, T, C and G  It was discovered that hydrogen bonds form between the different bases Remember Chargaff’s discovery A=T and C=G  Principal of Base Pairing - A always binds to T and C always bind to G  The pairs bind in this manner due to their size and hydrogen bonding.

21. The DNA Molecule

22. DNA Replication  The process of copying DNA within a cell  Occurs within the nucleus of the cell  3 steps 1. DNA Helicase breaks hydrogen bonds between base pairs - Replication Fork- the point at which 2 chains separate 2. Each chain serves as a template for a new nucleotide chain - DNA polymerase binds to the separated chains and adds corresponding base pairs in available spots 3. 2 identical molecules of DNA are formed - Semi-conservative process (1 original and 1 new strand of DNA results)

23. DNA Replication Continued…  This is a process that occurs spontaneously and at many point (makes it very fast!)  When the replication is complete, the cell is ready to undergo cell division

24. http://www.youtube.com/watch?v=hfZ8o9D1tus&feature=related

25. RNA (ribonucleic acid)  DNA is the mother copy of the recipe for making proteins.  DNA must be copied and edited to make proteins.  How does this happen?  With the production of RNA (transcription) and then RNA’s production of protein (translation).  Structure  5 carbon sugar (ribose)  Phosphate group  Nitrogenous Base (A-adenine, U-uracil, G-Guanine, C- cytosine)

26. Transcription  The process of copying a DNA into RNA  3 steps 1. RNA polymerase recognize a start site on the DNA causing the DNA to unravel 2. The RNA polymerase uses one of the strands as a template and forms complementary base pairs (C pairs with G and A pairs with U –Uracil) 3. Once transcription is complete, the new RNA strand separates from the DNA and the DNA helix zips together again

28. Transcription Continued…  Produces 3 different types of RNA 1. Messenger RNA (mRNA) - carries copies of instructions for copying amino acids into proteins - Serves as “messengers” from DNA to rest of the cell 2. Ribosomal RNA (rRNA) - Proteins are assembles here (make up the ribosome) 3. Transfer RNA (tRNA) - brings amino acids from the cytoplasm to a ribosome to help create a protein http://www.youtube.com/watch?v=NJxobgkPEAo

29. Translation  The process that converts, or translates, mRNA into proteins – Protein Synthesis  The language of nucleic acids  Codons- the 3 letter sequence of nucleotides or “words” that code for a particular amino acid.  Start codon – starts translation (AUG – methionine)  Stop codon – stops translation (UAA, UAG and UGA)

30. Translation Process  The mRNA is carried out of the nucleus and into the cytoplasm to the rRNA which is located in the ribosome  The codons of the mRNA match to the complimentary anti-codon of tRNA which also is carrying an amino acid  As more and more tRNA’s are matching up with the corresponding mRNA’s, more amino acids are coming into contact  The ribosome breaks the bond between the amino acids and the tRNA and links the amino acids together  This process of creating proteins is known as Protein Synthesis

31. http://www.youtube.com/watch?v=41_Ne5mS2ls&NR=1

32. Mutations  A change in DNA that affects the genetic information.  There is a series of proofreading and repair processes carried out by enzymes  What causes mutations?  Errors in replication  Mutagens – chemicals, radiation (UV, X-ray)

33. Types of Mutations  Gene mutations 2 types 1. Point mutations – 1 nucleotide is substituted for another (changes the amino acid) 2. Frameshift mutations – involves the insertion or deletion of a nucleotide (changes the amino acid sequence) Ex) THE CAT ATE THE RAT (if you remove the first E…) THC ATA TET HER AT (the letters now don’t make sense)

35. Mutations Continued…  Chromosomal mutations  Occurs during meiosis when chromosomes don’t exchange DNA properly  Causes 2 situations called gene duplication or translocation  Impact  Depending on the mutation, it could cause a change in phenotype of the individual or in the offspring