Honors Biology * The Race to Discover DNA

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Biology – DNA The Secret Code Notes with answers
1. What type of biomolecule (macromolecule) is DNA?
Nucleic Acid
2. What does DNA stand for?
Deoxyribonucleic Acid
3. What are the monomers of DNA called? Draw and Label one.
Nucleotides: 5 carbon sugar (deoxyribose), phosphate group, nitrogenous base
Phosphate group
Deoxyribose
Nitrogenous base
4. What is the overall shape of DNA called? Draw it.
A twisted ladder or “Double Helix”
5. What is the backbone of DNA made of?
Alternating 5 carbon sugars (deoxyribose) and phosphate groups
6. What are the rungs of DNA made of?
Nitrogenous bases
7. What are the 4 nitrogenous bases found in DNA? How do they pair up with each
other? Adenine, Thymine, Guanine, and cytosine.
Adenine always pairs with thymine. Guanine always pairs with cytosine.
A=T
G=C
8. Which bases are purines?
Adenine and Guanine
9. Which bases are pyrimidines?
Thymine and Cytosine
C
G
A
T
A
T
G
C
A
C
G
10. Label the missing bases
11. What is DNA replication?
T
The process of DNA making a copy of itself so that every cell gets an exact copy
of the genetic material.
12. What are the 3 steps of DNA replication and briefly describe what is happening
during each step? What enzyme is involved in each step?
Step 1: The parent DNA molecule unzips. The complimentary strands separate with
the help of an enzyme called DNA helicase.
Step 2: New nucleotides are added. Each parent strand serves as a template that
determines the order of the new bases being added. DNA polymerase adds the bases.
Step 3: The new nucleotides are attached to each other to close the gaps and to create
two new daughter strands of DNA that is identical to the parent strand. DNA Ligase
closes the gaps.
13. Why is DNA replication called semi-conservative?
Each “daughter” DNA molecule contains one parent strand and one new copied
strand.
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