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DNA Practice Test KEY
NAME __________________________
Test Section
HISTORY of DNA
Structure of DNA
DNA Replication
RNA
Protein Synthesis
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History of DNA
For each of the scientists below, write down what they contributed to the investigation of DNA’s function and
structure.
Griffith – Discovered that NON-LETHAL bacteria can be transformed into LETHAL Bacteria by being mixed
with heat-killed lethal bacteria cells.
Avery – Determined that DNA is the molecule of heredity, NOT PROTEIN.
Hershey and Chase – Supported Avery’s results by demonstrating that DNA is the material of heredity in
bacteriophages
Franklin and Wilkins – Took an X-ray diffraction photo that helped in determining the structure of DNA
Chargaff – Determined that in DNA the bases Adenine and Thymine are present in equal amounts, and the
Guanine and Cytosine are also present in equal amounts.
Watson and Crick – Discovered the structure of DNA and how it replicates.
For each of the scientists below, describe their experiment.
Griffith – Injected mice with 1 of 4 pneumonia bacteria. The four types that he used were Living Non-Lethal
Strain of Bacteria, Living Lethal Bacteria, Heat Killed Lethal Bacteria, and Heat Killed Lethal bacteria mixed
with Living Non-Lethal Bacteria.
Avery – Took the Heat Killed bacteria cell s of the same strand from Griffith’s experiment and treated them
with enzymes to create 4 different extracts. Each extract contained only one type of molecule – Protein,
DNA, Lipids, or Carbohydrates. He then mixed each of the extracts with living non-lethal bacteria and
tested for lethality on mice.
Hershey and Chase – Used bacteriophages grown in radioactive phosphorus and radioactive sulfur to track
what part of the bacteriophage virus entered into the bacteria cells to create more virus.
Franklin and Wilkins – Studied the structure of DNA by taking X-Ray Diffraction photos of crystallized DNA.
Structure of DNA
What three things make up a nucleotide?
What do 5’ and 3’ stand for?
They are the labels to the unbound ends of a single DNA Strand
Draw and Label a DNA Strand with the following sequence on the top strand:
5’ – AGTGGTGCCGTAAA – 3’
Use Chargaff’s rules to make the complimentary strand below.
5’ – T A T A A A A G C C G A T T G C C – 3’
3’ – A T A T T T T C G G C T A A C G G – 5’
If you are given a segment of DNA, and are told that Cytosine makes up 16% of the segment, what are the
percentages of the other bases?
C = 16%
G = 16%
A = 34%
T = 34%
DNA Replication
In the spaces below, LIST the 4 enzymes involved with DNA Replication AND THEN explain what each enzyme
does.
Enzyme #1 – DNA HELICASE
Enzyme # 1 Function – Breaks the hydrogen bonds between the nucleotides causing the DNA molecule to
unwind and split into the two different strands.
Enzyme #2 – DNA POLYMERASE
Enzyme # 2 Function – Binds to the original DNA strand at the end of an RNA Primer and moves in the 5’ to 3’
direction of the original strand. As it moves it makes the new complimentary strand by base pairing to the
original strand. After creating the new strand, Polymerase will remove the RNA Primers and replace it with
DNA Bases.
Enzyme #3 – RNA PRIMASE
Enzyme # 3 Function – Lays down a small strip of RNA Primer so that DNA Polymerase can bind to the
original strand and complete its function.
Enzyme #4 – DNA LIGASE
Enzyme # 4 Function – Repairs any broken bonds in the Sugar Phosphate Backbone, as well as, the hydrogen
bonds between the bases. This causes the DNA strand to coil into the double helix.
Explain how the LAGGING Strand of DNA is replicated.
The lagging strand is the strand of original (template)DNA whose direction of synthesis is opposite to the
direction of the growing replication fork. Because of its orientation, replication of the lagging strand is
more complicated as compared to that of the leading strand.
The lagging strand is synthesized in short, separated segments. On the lagging strand template,
a primase "reads" the template DNA and initiates synthesis of a short complementary RNA primer. A DNA
polymerase extends the primed segments, forming Okazaki fragments. The RNA primers are then removed
and replaced with DNA, and the fragments of DNA are joined together by DNA ligase.
Listed below are all the main parts/labels for a DNA Replication Fork. Label the provided picture below.
RNA
For each of the types of RNA listed below, explain what its function is.
Messenger RNA - mRNA – carries a message from the DNA to the cytoplasm
Transfer RNA - tRNA – transports amino acids to the mRNA to make a protein
Ribosomal RNA - rRNA – make up ribosomes, which make protein.
How is RNA different from DNA?

RNA is almost exactly like DNA, except:
–
Contains a ribose sugar, instead of a deoxyribose sugar (hence the name…)
–
Contains uracil instead of thymine.
–
RNA is single-stranded, not double-stranded (usually…)
Protein Synthesis
Explain the process of transcription:
Transcription proceeds in the following general steps:
1. RNA polymerase binds to the promoter sequence of DNA.
2. RNA polymerase creates a transcription bubble, which separates the two strands of the DNA helix.
This is done by breaking the hydrogen bonds between complementary DNA nucleotides.
3. RNA polymerase adds matching RNA nucleotides to the complementary nucleotides of one DNA
strand.
4. RNA sugar-phosphate backbone forms with assistance from RNA polymerase to form an RNA
strand.
5. Hydrogen bonds of the untwisted RNA-DNA helix break, freeing the newly created mRNA strand.
6. If the cell has a nucleus, the RNA may be edited through the process of splicing.
7. The mRNA moves out of the nucleus.
Explain the process of translation:
1. A ribosome on the rough endoplasmic reticulum attaches to the mRNA molecule.
2. A transfer RNA molecule arrives. It brings an amino acid to the first three bases (codon) on the
mRNA. The three unpaired bases (anticodon) on the tRNA link up with the codon.
3. Another tRNA molecule comes into place, bringing a second amino acid. Its anticodon links up with
the second codon on the mRNA.
4. A peptide bond forms between the two amino acids.
5. The first tRNA molecule releases its amino acid and moves off into the cytoplasm.
6. The ribosome moves (translocates) along the mRNA to the next codon.
7. Another tRNA molecule brings the next amino acid into place.
8. A peptide bond joins the second and third amino acids to form a polypeptide chain.
9. The process continues. The polypeptide chain gets longer.
10. This continues until a termination (stop) codon is reached.
11. The polypeptide is then complete.
You have been given the following DNA Sequence:
5’ – T A C | GAC | CCC | AAG| T A A | T C C | T A G – 3‘
(7pts) Using base pairing determine the mRNA strand that would be made during transcription.
5’ - A U G | C U G| G G G| U U C| A U U| A G G| A U C - 3’
(7pts) Using the mRNA strand that YOU just wrote in the last question and the chart below, TRANSLATE the
mRNA into a strip of amino acids.
5’ – Met | Leu | Pro | Phe | Ile | Arg | Ile - 3’