Name__________________________ Class _______________ Date _____________


Reading Guide

Section 12.1 Identifying the Substance of Genes (pp.338-343)


Bacterial  Transformation s the process by which one strain of bacteria c

  1. What is bacterial transformation?



  1.  What was the conclusion from Avery’s experiments?



Bacterial Viruses

  1. What is a bacteriophage?




  1. Circle the letter of each part that makes up a bacteriophage.

a. lipid coat                                               c. carbohydrate core

b. protein coat                                           d. DNA core


  1. Hershey and Chase concluded that the genetic material of the bacteriophage was __________________________.



The Role of DNA

6. List the three critical things that the DNA that makes up genes are known to do.



b. G


c. Genes had to be easily copied.


Section 12.2 The Structure of DNA (pp. 344-348)

The Components of DNA

  1. What is DNA?



  1. What are the building blocks of nucleic acids?



  1.  Identify the components of a nucleotide in the diagram below as 5 –carbon sugar, phosphate group or a nitrogen base. Label the bases as either purines or pyrimidines.


Text Box: pyrimadines


Text Box: purines



  1. Adenine, guanine, cytosine, and thymine are four kinds of ___________________

bases in DNA.


  1. Is the following sentence true or false? The nucleotides must be joined together in a specific order. ______



Solving the Structure of DNA

  1. Use figure 12-5. Is the following sentence true or false? Adenine and guanine are larger molecules than cytosine and thymine because they have two rings in their structure. ______


  1. According to Chargaff’s rules, the percentages of _____________________are equal to thymine and the percentages of _______________________are equal to guanine in the DNA molecule.


  1. Rosalind Franklin’s work with X-ray diffraction showed that the DNA molecule is shaped like a(an) ________________________and contains ______________ strands.


  1. How did Watson and Crick describe the structure of DNA?




The Double –Helix Model

  1. What does a double-helix look like?




  1. What is meant by “antiparallel” strands?


  1. What holds the two strands of DNA together?



  1. Look at figure 12-7, how many hydrogen bonds are between C and G?  between A and T?



  1.  Is the following sentence true or false? According to the principle of base pairing,

hydrogen bonds could form only between adenine and cytosine. _________



Section 12.3 DNA Replication (pp. 350-353)

Copying the Code

  1. Why are the strands of a DNA molecule said to be complementary?



  1. What is the first step in eukaryotic DNA replication?



  1. If the base sequence on a separated DNA strand is CGTAGG, what will the base sequence on its complementary strand be?



  1. What enzyme joins individual nucleotides to produce the new strand of DNA?



  1. What enzyme makes it less likely that DNA will be lost from telomeres during replication?



26.  How does this enzyme work?



27.  Does DNA replication take place in the same direction along both strands of the DNA molecule that is being replicated? Explain your answer. (Hint: Look at the illustration of DNA replication in your textbook.)



28.  Label the nitrogenous bases, replication fork, DNA polymerase, the original strand, and the new strand.




Replication in Living Cells


29.  Complete the table to compare and contrast DNA replication in prokaryotes and eukaryotes.







Location of DNA





Amount of DNA





Starting point(s) for replication