DNA and RNA

1. DNA and RNA Chapter 12 Notes

2. April 6, 2010: “D” Day • Objective: To understand the importance of the structure of DNA • Do Now: What is the basic structure of DNA? • Journals Due Now • DNA – “The Double Helix” Packet • Human Genetic Disorders Presentations Next Week!

3. April 6, 2010: “D” Day • Objective: To study a human genetic disorder. • Do Now: How is your genetic disorder inherirted? • Journals Due Now • Continue Research/Presentation • Human Genetic Disorders Presentations Next Week!

4. April 7, 2010: “E” Day • Objective: To understand the importance of the structure of DNA. • Do Now: What is meant by the term “complementary” when referring to the 2 strands of DNA? • Did you hand in your Journal? • Chapter 12 Notes • 12-1 Guided Read

5. April 9, 2010: “A” Day • Objective: To understand the importance of the structure of DNA. • Do Now: Where can DNA be found? • Did you hand in your Journal? • Check in DNA- “Double Helix” Coloring packet • Today - DNA Extraction Lab

6. April 6, 2010: “D” Day • Read 21.1 and 21.3 and Take your own notes • Complete Element/Compound Structure & Symbol Packet (entire page 1 and odds for the rest)

7. Griffith and Transformation • In 1928, British scientist Frederick Griffith was trying to figure out how bacteria make people sick • Griffith isolated two different strains, or types, of pneumonia bacteria from mice. • Both strains grew in culture plates in his lab, but only one caused pneumonia • The disease-causing strain of bacteria grew into smooth colonies on culture plates • The harmless strain produced colonies with rough edges

9. Griffith’s Experiments • When Griffith injected mice with the disease-causing strain of bacteria, the mice developed pneumonia and died. • When mice were injected with the harmless strain, they didn't get sick at all. • To find out if the bacteria might create a poison, he took these cells, heated the bacteria to kill them, and injected the heat-killed bacteria into mice. • The mice survived, suggesting that the cause of pneumonia was not a chemical poison released by the disease-causing bacteria.

10. Griffith’s Transformation • Next he mixed his heat-killed, disease-causing bacteria with live, harmless ones and injected the mixture into mice. • To Griffith's amazement, the mice developed pneumonia and many died. • When he examined the lungs of the mice, he found them filled with the disease-causing bacteria. • Somehow the heat-killed bacteria had passed their disease-causing ability to the harmless strain. • Griffith called this transformation because one strain of bacteria (the harmless strain) had apparently been changed permanently into another (the disease-causing strain).

11. Hypotheses • Griffith hypothesized that when the live, harmless bacteria and the heat-killed bacteria were mixed, some factor was transferred from the heat-killed cells into the live cells. • That factor, he hypothesized, must contain information that could change harmless bacteria into disease-causing ones. • Furthermore, since the ability to cause disease was inherited by the transformed bacteria's offspring, the transforming factor might be a gene.

12. Avery’s Experiments • In 1944, biologist Oswald Avery and peers repeated Griffith's work to find the molecule in the dead bacteria was most important for transformation. • If transformation required just one molecule, that might well be the molecule of the gene. • Avery made an extract from the heat-killed bacteria and treated it with enzymes that destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNA. • Transformation still occurred!These molecules could notbe responsible for the transformation.

13. Avery and DNA • Avery and the other scientists repeated the experiment, using enzymes that would break down DNA. • When they destroyed the nucleic acid DNA transformation did not occur. • He concluded DNA is the transforming factor and that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next!

14. The Hershey-Chase Experiment • Scientists are a skeptical group so further studies were done to prove DNA was it! • In 1952 by two American scientists, Alfred Hershey and Martha Chase did one of these studies. They worked with viruses, nonliving particles smaller than a cell that can infect living organisms. • Specifically they worked with bacteriophages.

15. Bacteriophages • One kind of virus that infects bacteria is known as a bacteriophage, which means “bacteria eater.” • Bacteriophages are composed of a DNA or RNA core and a protein coat. • When a bacteriophage enters a bacterium, the virus injects its genetic information into he cell . • The viral genes produce many bacteriophages, and they destroy the bacterium. • When the cell splits open, hundreds of new viruses burst out.

16. Bacteriophage

17. Hershey and Chase mixed radioactive marked viruses with bacteria. Then, they waited a few minutes for the viruses to inject their genetic material. Next, they separated the viruses from the bacteria and tested the bacteria for radioactivity. Nearly all the radioactivity in the bacteria was from phosphorus (32P), the marker found in DNA, and not the sulfur (35S) which was on the proteins.

18. Hershey and Chase • Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein. • Their study supported Avery’s findings!

19. The Components and Structure of DNA • Now scientists wondered how DNA could do the three critical things that genes were known to do: • genes had to carry information from one generation to the next • they had to determining the heritable characteristics of organisms • genes had to be easily copied

20. Structure of DNA • DNA is a long molecule made up of units called nucleotides. • Each nucleotide is made up of three basic components: • a 5-carbon sugar called deoxyribose, • a phosphate group • nitrogenous (nitrogen-containing) base • There are four kinds of bases * Remember Py – Cy – Thy!

21. How do they fit together? • Scientists knew DNA was made of nucleotides, but still did not know how they fit together • In the 1950’s all we knew was Chargaff’s rules • Erwin Chargaff showed that the percentages of guanine and cytosine in DNA are almost equal. The same is true for adenine and thymine.

22. Chargaff’s Rules % A = %T % C = %G …but nobody knew why…

23. April 29, 2009: “B” Day • Objective: To understand how genes are regulated • Do Now:What is an operon? Why do you think scientists use the lacOperon as a model? • Today – • Finish “Pandora’s Box” • Answer Pandora’s Box reflection questions – hand in! • Begin Virus Packet – define the words/terms using dictionary, book, or online sources

24. DNA and RNA Replication 12-2 Notes

25. DNA • DNA is present in such large amounts in many tissues that it's easy to extract and analyze, but… • Where is DNA found in the cell? • How is it organized? • Where are the genes that Mendel first described?

26. Prokaryotic Chromosomes • Prokaryotic cells lack nuclei so their DNA molecules are in the cytoplasm. • Most prokaryotes have a single circular DNA molecule called the “chromosome”

27. Eukaryotic Chromosomes • Many eukaryotes have as much as 1000 times the amount of DNA as prokaryotes, located in the cell nucleus. • The number of chromosomes varies widely from one species to the next. • For example, human cells have 46 chromosomes, Drosophila cells have 8, and giant sequoia tree cells have 22.

28. DNA Length • DNA molecules are surprisingly long. • The chromosome of E. coli, contains 4,639,221 base pairs. • The length of such a DNA molecule is roughly 1.6 mm, which doesn't sound like much until you think about the small size of a bacterium (only 0.0001mm long) • To fit inside the DNA molecule must be folded into a space only one one-thousandth of its length.

29. Chromosome Structure • The DNA in eukaryotic cells is packed even more tightly. The nucleus of a human cell contains more than 1 meter of DNA. • Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called chromatin. • Chromatin consists of DNA that is tightly coiled around proteins called histones, • Together, the DNA and histone molecules form a beadlike structure called a nucleosome. • Nucleosomes pack with one another to form a thick fiber, which is shortened by a system of loops and coils.

30. Chromosome Structure

32. Eukaryotic Chromosome Structure

33. Chromosome Structure (cont.) • During most of the cell cycle, these chromatin fibers are dispersed in the nucleus so that individual chromosomes are not visible. • During mitosis, the fibers of each chromosome are drawn together, forming the tightly packed chromosomes you can see through a light microscope in dividing cells. • The tight packing of nucleosomes may help separate chromosomes during mitosis.

34. What do nucleosomes do? • Nucleosomes seem to be able to fold enormous lengths of DNA into the tiny space available in the cell nucleus. • This is such an important function that the histone proteins themselves have changed very little during evolution—probably because mistakes in DNA folding could harm a cell's ability to reproduce.

35. DNA Replication • When Watson and Crick discovered the structure of DNA, there was one remarkable aspect that they recognized immediately. • The structure explained how DNA could be copied, or replicated. • Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing. • Because each strand can be used to make the other strand, the strands are said to be complementary. • If you could separate the two strands, the rules of base pairing would allow you to reconstruct the base sequence of the other strand.

36. DNA Replication • Replication Lab • Replication of DNA “Active Reading”

37. April 27, 2009: “E” Day • Objective: To understand how genes are regulated • Do Now: What is a DNA promoter and what does it do? • Today – • Read “Gene Regulation” packet and answer questions. Provide EVIDENCE of reading (such as notes in margin, highlighting important information) • Complete for HW • Tomorrow 12-5 Guided Read and “Gene” packet will be collected!

38. April 30, 2009: “C” Day • Objective: To understand the structure and function of viruses. • Do Now: What are some diseases spread by viruses? How are they treated? • Today • INFECT EACHOTHER • Begin Viruses packet Flu Virus HIV Virus

39. May 1, 2009: “D” Day • Objective: To understand the structure and function of viruses. • Do Now: Are viruses alive? Why or why not? • Today • Hand in “Bonus” assignment • Complete Viruses packet • TEST next Wednesday on Gene Expressions, Mutations,and Viruses Flu Virus HIV Virus

40. May 4, 2009: “E” Day • Objective: To understand the structure and function of Bacteria. • Do Now: What are some differences betweenbacterial cells and plant andanimal cells? • Today • Hand in Virus Packet Questions • Bacteria Packet – Complete for Homework • TEST Wednesday!