Name: ______Date: ______Block: ______

DNA STRUCTURE AND REPLICATION LAB

STATION 1:DNA Extraction from a Strawberry

Introduction:

DNA is present in the cells of all living organisms. This procedure is designed to extract DNA from a strawberry in enough quantities to be seen.

Pre-lab Questions:

  • One way to purify a molecule is to get rid of everything but the molecule. If we want to isolate DNA from a strawberry, what do you have to get rid of in the cell?

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  • What can scientists do with the DNA once it has been purified? Give some real world examples.

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Questions and Observations:

Answer the following questions based off what you observed during the lab.

  1. What does mashing the strawberry do? ______
  2. What do you think the extraction solution is? What does it do to the strawberry?

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  1. What is being filtered out? What is going through the filter? ______

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  1. What do you think the ethanol does? Why do we want it cold? ______

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  1. What do you see in the top portion of the liquid? What do you think it is? ______

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Part 2: DNA and Chromosome Structure

Use your notes to answer the following questions

  1. Where in eukaryotic cells is DNA found? ______

Where in prokaryotic cells is DNA found? ______

  1. What makes up a nucleotide? ______
  2. What is the importance of the phosphate and sugar group in DNA? ______
  3. What part of a DNA molecule is responsible for the genetic code? ______
  4. What is the difference between purines and pyrimidines? Why do they bond with each other? ______

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  1. Which nitrogen bases are purines? ______
  2. Which nitrogen bases are pyrimidines? ______
  3. How many hydrogen bonds hold together adenine and thymine? ______
  4. How many hydrogen bonds hold together cytosine and guanine? ______
  5. Complete the following strand of DNA by placing the letter of the correct nitrogenous base on the line provided

5’ / C / C / A / G / T / A / G / T / T / 3’

Station 3: Online DNA Lab

Watch the animations and answer the following questions

ANIMATION: How Nucleotides are added in DNA replication?

  1. List the proteins/enzymes involved in the process of replication. ______

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  1. How does replication start? Who prevents the unwound DNA for twisting back?

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  1. Which enzyme is the key player in replication? What is this enzyme’s limitation? How is this limitation overcome? ______

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  1. Why do the two strands of the helix have to be elongated by two slightly different mechanisms? ______

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  1. Explain the elongation stage of replication – your answer should include a discussion of the leading strand, lagging strand, Okazaki pieces and RNA primer. ______

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ANIMATION: DNA Replication Fork

  1. Draw a picture of the replication fork and label all the components therein.
  1. How are Okazaki fragments on the lagging strand joined into one continuous strand?

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Part 4: DNA Replication (the whole picture)

Watch the animations and answer the followingpop quiz questions.

Pop Quiz: Answer the following pop quiz questions that follow the video above.

  • Which biomolecule is the carrier of hereditary information? ______
  • Which of these models best fits the correct model postulated by Watson & Crick?

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  • Identify the atom on the thymidine where the nucleophile attack occurs.
  • What type of molecule is the primer (in blue)? ______
  • In what direction is DNA synthesized? ______

Part 5: DNA Replication Use your notes to answer the following questions

  1. When and why does DNA need to replicate? ______

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  1. How do base-pairing rules make DNA replication possible? ______

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  1. What are Okazaki fragments? Why do they form? ______

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  1. DNA synthesis always goes from ______‘to ______‘.
  2. What is the role of Helicase in DNA replication and why is it so important?

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  1. What is the role of DNA polymerase I and polymerase III in DNA replication?

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  1. What is the role of DNA Ligase in DNA replication and why is it so important?

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  1. How do eukaryotes speed the process of replication – since they have multiple chromosomes that are very long?______

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