Name: __Answer Key___ Pretest score: ________/ 41Posttest score: ________/ 41

Pretest Ch 12: DNAMatching. Match the word on the right with the correct definition on the left.

1. ___P___ the structure that forms when DNA A. complementary base pairis “unwound” to be copied B. DNA

2. ___I___ the strand that takes longer to copy, C. DNA helicaseis copied in fragments, not all at once D. DNA polymerase

3. ___O___ besides sugar, the other molecule that E. deoxyribosemakes up the “sides” of the DNA F. double helixmolecule; PO43- G. enzyme

4. ___A___ A & T or G & C when they match up H. hydrogen bondI. lagging strand

5. ___F___ the twisted ladder shape that DNA forms J. leading strand K. mutation

6. ___E___ the 5-carbon sugar that makes up the L. nitrogenous base “sides” of the DNA molecule M. nucleotide

7. ___K___ when something goes wrong with N. Okazaki FragmentsDNA replication O. phosphate group

8. ___B___ molecule that controls cell functions P. replication fork by making proteins Q. semi-conservative

9. ___J___ the strand of DNA that is copied as one big piece, instead of small fragments10. __H__ what holds the nitrogen bases are held together to form the “rungs” of the DNA ladder11. ___D___ enzyme responsible for making new DNA strands

12. ___G___ chemical that controls a function in the cell or body by running a chemical reaction 13. ___M___ the subunit of DNA; DNA is made of many of these put together; it has three parts14. ___Q__ DNA replication is called this because, for the two new strands, one is

the original and one is a copy

15. ___L___adenine, cytosine, guanine and thymine; they make up the “rungs” of the DNA ladder16. ___C___enzyme responsible for “unzipping” the DNA molecule so it can be copied17. ___ N___small pieces on the lagging strand that are “stitched” together

Prokaryotic DNA replication is different than eukaryotic. How…?18. What shape does prokaryotic DNA have?

Circular rather than strands19. How many replication forks does it have?

only 2…starts at one point and goes both ways around the circle (eukaryotes have many replication forks)20. Describe the process of prokaryotic DNA replication.

starts at one point and goes both ways around the circle DNA replication really happens in three steps. Describe each step and the enzyme involved:

21. Step 1:DNA Helicase

“unwinds” the DNA molecule (breaks hydrogen bonds)23. Step 2:

DNA P olymerase adds new complementary base pairs (A with T, G with C)25. Step 3:

There’s one strand (leading strand) that gets copied as one long piece. There another (lagging strand) that is “upside down” (antiparallel) and gets copied in pieces (Okazaki fragments) and those get put together by DNA Ligase.

DNA Polymerase “rezips” and checks the two new molecules for mistakes.Here is a picture of the DNA molecule and a close up of its structure. Identify the following….

27. _ Double helix__ the shape of the whole structure

28. __phosphate__ the little black circle

29. __deoxyribose (sugar)_ the pentagon

30. _nitrogen base__ the

27.

A29.

30.

30.

32.28.

G

T

A

rectangle

31. _covalent bond__ the lines in between the circles,

pentagons and rectangles

32. __hydrogen bond_ the lines between rectangles33. __nucleotide_ the structure inside the rectangle

34. __complementary base pair__ the structure inside the rectangle

35. Fill in the matching letters in the column of rectangles on the left.From top to bottom… A G T A C G

Describe each of the following scientists contribution to the discovery of the structure and function of DNA:

36. Griffiths: (1928): What part of bacteria makes people sick? Mice that got mix of heat killed pneumonia bad strain + good strain died. Called this transformation, and said it was because of a gene passed to new bacteria.

33.

34.C

G

37. Avery: (1944): Repeated above experiment to find exactly what particle makes people sick. Isolated many particles…fats (lipids), carbs, proteins…bacteria still transformed. Destroyed nucleic acids, bacteria did not transform. Therefore nucleic acid must be why bacteria get people sick.38. Hershey/Chase: (1952): virus called bacteriophage…protein coat surrounding DNA core. Is it protein or DNA? Used radioactive isotopes on both parts and let infect bacteria. Radioactive protein had no results (no radioactivity in cell). Radioactive DNA was found inside cell, so its DNA makes us sick.

39. Franklin: (1952): X-ray of DNA

40. Chargaff: (1952): showed % adenine (A) = % Thymine (T) and % guanine (G) = % cytosine (C) for any living thing41. Watson/Crick: (1953): saw Franklin’s X-ray and discovered double helix.