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Replication of DNA
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DNA, RNA, Protein Synthesis Name_______________________________ Homework #2: DNA Replication Date ___________________
Fill in the Blanks: __________________________1. The process of forming an exact copy of the DNA molecule. __________________________2. What type of bond holds the nitrogen bases to one another across the middle
of the helix? __________________________3. What type of bond connects one nucleotide to the next nucleotide? __________________________4. In what part of the cell does replication occur? __________________________5 During replication, the two nucleotide chains ___5___ and each chain will serve
as a ___6___ for the production of a new DNA chain. The sites where new nucleotides are added are called ___7___.
__________________________6. __________________________7. __________________________8. When replication occurs, it takes place at multiple sites along the molecule
called ___8___. __________________________9. The first step in replication is to break the ___9___ bonds between the ___10___.
This is accomplished by the enzyme ___11___. _________________________10. _________________________11. _________________________12. _________________________13. _________________________14. _________________________15. _________________________16. A change in the base sequence of DNA is called a ___16___. _________________________17. _________________________18. _________________________19.
The copying of the DNA molecule is a fairly reliable process. As new nucleotides are added, there is an error rate of about 1 in ___12___ base pairs. The enzyme, ___13___ proofreads the new strand and looks for errors. If a mistake is found, this same enzyme removes the erroneous ___14___ and replaces it with another. After the proofreading, there is a final error rate of only 1 in ___15___ base pairs.
Several enzymes are involved in repairing damaged DNA. Enzymes called ___17___ cut out damaged sections of DNA. The enzyme ___18___ fills the resulting gaps with new nucleotides. ___19___ then seal the free ends, making the strand complete.
Copyright © 2013 Amy Brown (aka Science Stuff)
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Short Answer: 1. What is the primary function of DNA? 2. Why is it so important that the DNA molecule be able to make copies of itself? 3. What are two functions of DNA polymerase during replication? 4. When a DNA molecule is replicated, what is the relationship between the original strand and the
newly formed strands of DNA? 5. What is meant by the “base-‐pairing” rules? 6. What is the advantage to the multiple sites of replication along the DNA molecule? Multiple Choice: ________1. The main enzyme of replication whose function is to link together individual nucleotides along
a template strand is called: (1) RNA polymerase (2) ligase (3) DNA polymerase (4) nuclease.
________2. When replication is complete, two _____ copies of the DNA molecule have been produced and the cell is ready to begin _____.
(1) different; growing (2) identical; growing (3) different; transcription (4) identical; cell division
________3. Each strand of the DNA molecule can be used to make another strand during replication. This is because the two sides are ______ to each other. (1) homologous (2) complimentary (3) identical (4) translatable.
________4. Which of the following might cause accidental damage or changes in existing DNA? (1) exposure to chemicals (2) radioactivity (3) x-‐rays (4) excessive exposure to
ultraviolet light (5) all of the above.
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True/False? _____________1. The process of DNA replication produces an identical copy of the original DNA strand. _____________2. Replication results in two copies of the DNA molecule. _____________3. The replication of DNA begins at one end of the molecule and proceeds to the other end. _____________4. DNA replication occurs simultaneously at many sites along the molecule, speeding up the
process of replication. _____________5. At the end of replication, each DNA molecule has one original strand and one new strand. _____________6. The primary purpose of replication is to produce new DNA strands that are very different
from the old strands. _____________7. Mutations always cause serious and harmful effects in the organisms in which they occur. _____________8. Mutations can sometimes be an advantage by making the organism slightly better suited
for its environment. _____________9. Damage to DNA can never be repaired. Label the parts of the drawing below. Include all of these terms: nucleotide, phosphate, sugar, nitrogen base, hydrogen bond, covalent bond, purine, pyrimidine, adenine, thymine, cytosine, guanine, DNA backbone. Copyright © 2013 Amy Brown (aka Science Stuff)
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Answers: Fill in the Blanks: 1. replication 2. hydrogen bonds 3. covalent bonds 4. the nucleus 5. separate 6. template 7. replication forks 8. origins of replication 9. hydrogen 10. nitrogen bases 11. helicase 12. 100,000 13. DNA polymerase 14. nucleotide 15. 10 billion 16. mutation 17. nucleases 18. DNA polymerase 19. ligases Short Answer: 1. The DNA is the storage area for the protein building instructions of the cell. 2. Whenever cells are preparing for mitosis or meiosis, The DNA must be copied exactly so that each
new cell will receive an identical copy of the complete genome. 3. DNA polymerase is the principle enzyme involved in DNA replication. These enzymes add the new
nucleotides to the newly forming strands of DNA. DNA polymerases also proofread the new strands as they are being made and will correct any errors that are found.
4. The newly formed strands are identical to the original, parental strands. 5. Adenine always pairs with thymine. Cytosine always pairs with guanine. These are referred to as
the base pairing rules. 6. The replication of DNA begins at many origins of replication along the DNA molecule. This speeds up
the process of replication. If replication started at one end and proceeded until it reached the other end, the process would be much slower.
Multiple Choice: 1. 3 2. 4 3. 2 4. 5
Copyright © 2013 Amy Brown (aka Science Stuff)
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True/False: 1. True 2. True 3. False 4. True 5. True 6. False 7. False 8. True 9. False
Created by Amy Brown – Science Stuff Copyright © 2013 Amy Brown (aka Science Stuff)
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