Answer Key___
Name: __
Pretest score: ________/ 40
Posttest score: ________/ 40
Pretest Ch 12: DNA
Matching. Match the word on the right with the correct definition on the left.
O___ the structure that forms when DNA
1. ___
is “unwound” to be copied
I
2. ___ ___ the strand that takes longer to copy,
is copied in fragments, not all at once
N___ besides sugar, the other molecule that
3. ___
makes up the “sides” of the DNA
molecule; PO43-
A___ A & T or G & C when they match up
4. ___
F___ the twisted ladder shape that DNA forms
5. ___
E___ the 5-carbon sugar that makes up the
6. ___
A. complementary base pair
B. DNA
C. DNA helicase
D. DNA polymerase
E. deoxyribose
F. double helix
G. enzyme
H. hydrogen bond
I. lagging strand
J. leading strand
K. mutation
“sides” of the DNA molecule
L. nitrogenous base
M. nucleotide
DNA replication
N. phosphate group
O. replication fork
K___ when something goes wrong with
7. ___
B___ molecule that controls cell functions
8. ___
P. semi-conservative
by making proteins
J___ the strand of DNA that is copied as one big piece, instead of small
9. ___
fragments
H__ what holds the nitrogen bases are held together to form the “rungs” of the
10. __
DNA ladder
D___ enzyme responsible for making new DNA strands
11. ___
G___ chemical that controls a function in the cell or body by running a
12. ___
chemical reaction
M___ the subunit of DNA; DNA is made of many of these put together; it has
13. ___
three parts
P__ DNA replication is called this because, for the two new strands, one is the
14. ___
original and one is a copy
L___adenine, cytosine, guanine and thymine; they make up the “rungs” of the
15. ___
DNA ladder
C___enzyme responsible for “unzipping” the DNA molecule so it can be copied
16. ___
Prokaryotic DNA replication is different than eukaryotic. How…?
17. What shape does prokaryotic DNA have?
Circular rather than strands
18. How many replication forks does it have?
2…starts at one point and goes both ways
around the circle (eukaryotes
have many replication forks)
19. 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:
20. Step 1:
DNA helicase
“unwinds” the DNA
molecule (breaks
hydrogen bonds)
22. Step 2:
DNA
polymerase adds
new complementary base pairs (A with T, G
with C)
24. Step 3:
DNA polymerase
“rezips” and checks the
two new molecules for
mistakes. 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).
Here is a picture of the DNA molecule and a close up of its structure. Identify the
following….
Double helix__ the
26. _
A
shape of the whole structure
phosphate__ the little
27. __
black circle
deoxyribose
(sugar)_ the pentagon
28. __
nitrogen base__ the
29. _
rectangle
covalent bond__ the
30. _
lines in between the circles,
pentagons and rectangles
hydrogen bond_ the
31. __
lines between rectangles
27.
28.
29.
31.
G
30.
T
A
C
G
32.
33.
26.
nucleotide_ the structure inside the rectangle
32. __
complementary base pair__ the structure inside the
33. __
rectangle
34. 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:
(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 since it was passed to new bacteria.
35. Griffiths:
(1944): Repeated above experiment to
find exactly what particle makes people sick.
Isolated many particles…fats (lipids), carbs,
proteins, RNA…bacteria still transformed.
Destroyed DNA, bacteria did not transform.
36. Avery:
Therefore DNA must be why bacteria get people
sick.
(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.
37. Hershey/Chase:
38. Franklin:
(1952): X-ray of DNA
(1952): showed % adenine
(A) = % Thymine (T) and % guanine
(G) = % cytoseine (C)…wondered
about structure
39. Chargaff:
(1953): saw
Franklin’s X-ray and
discovered double helix.
40. Watson/Crick: