1.  MONDAY: Study the “old dead people” from this unit!  TUESDAY: QUIZ on DNA structure  WEDNESDAY:  THURSDAY:  FRIDAY: TEST—DNA

4.  Biochemist  Discovered that the amount of A (Adenine) equaled the amount of T (thymine) in ANY DNA sample.

5.  Also that the amount of G (Guanine) equaled the amount of C (cytosine) in ANY DNA sample.  This idea is called “Chargaff’s Rule”

6.  First person to “photograph” DNA.  Used an X-Ray machine to take the picture.  Her photograph revealed an “X” shaped pattern.

8.  This is her famous photograph.  The angle of the “X” shape suggested that there were 2 strands, not 1!

9.  At the same time Franklin was taking pictures of DNA, Watson and Crick were trying to make a 3D model of DNA.

10.  As soon as Watson saw Franklin’s photograph they figured it out.  They discovered that DNA was actually 2 strands twisted around each other.

11.  A Double Helix looks like a twisted ladder, or a spiral staircase.  The double helix model explains Chargaff’s rule of base pairing and how the two strands of DNA are held together!

12.  The 2 strands of DNA run in opposite directions.  The base pairs meet in the middle.

13. Start End Stop End Start End Stop End Adenine Thymine Guanine Cytosine Antiparallel Lines

14.  The two strands of DNA are held together by hydrogen bonds!  The bonds form between certain base pairs.  Why would you want a WEAK bond to hold together something as important as DNA?

15. Hydrogen Bonding is happening at the dotted lines!

16. Watson and Crick showed that hydrogen bonding only happens between certain base pairs… Adenine and Thymine Guanine and Cytosine This perfectly fit between A-T and G-C nucleotides is called base pairing!

19. 1.What are the letters used to represent the nitrogen bases? 2. Which base pairs up with (T)? 3.What kind of chemical bond holds nitrogen bases together? 4.What kind of sugar is in DNA?

20.  MONDAY: Homework—DNA Base Pairing and Structure Sheet  TUESDAY: Homework—DNA Replication Sheet  WEDNESDAY: Homework—What is a DNA mutation?  THURSDAY: Quiz  FRIDAY:

21. Parts of DNA Phosphate Backbone Deoxyribose (Sugar) Nitrogen Base Adenine Thymine Guanine Cytosine

22. These three molecules make up a NUCLEOTIDE. Many NUCLEOTIDES make up a NUCLEIC ACID.

26. Phosphate Group, Deoxyribose, Nitrogen Base Pairs—Adenine, Guanine, Thymine, Cytosine

27. H-bonds hold the paired bases together. Because the bonds are weak the two strands of DNA are easily separated.

28. Chargaff: (A) = (T) and (G) = (T) Franklin: 2 strands, maybe a spiral? Watson and Crick: Double helix, base pairing

29. DNA is too small to be examined with a light microscope—the only microscope available at the time.

30. Two Antiparallel strands that are connected by hydrogen bonds between nitrogenous bases…A = T and G = C

31. Watson and Crick’s model showed a double helix with (T) and (A) paired together…so, YES.

32.  http://www.apsnet.org/edcenter/K- 12/TeachersGuide/DNA_Easy/Pages/Background.aspx http://www.apsnet.org/edcenter/K- 12/TeachersGuide/DNA_Easy/Pages/Background.aspx  http://www.nature.com/scitable/topicpage/discovery- of-dna-structure-and-function-watson-397 http://www.nature.com/scitable/topicpage/discovery- of-dna-structure-and-function-watson-397  http://sites.google.com/site/aninditosen2004/home http://sites.google.com/site/aninditosen2004/home

33. Put your homework on your desk please!