Lecture 15 Class: DNA Structure
Starter:
You would expect to find ___________________, an enzyme involved in DNA
replication, in the:
A. Nucleus, breaking phosphodiester bonds
B. Nucleus, forming phosphodiester bonds
C. Nucleus, breaking hydrogen bonds
Frederick Griffith discovers transformation
Known: Cells could pass on traits to offspring
Unknown: What part of a cell is used to pass on the information?
Experimental organism:
Conclusion:
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Alfred Hershey and Martha Chase demonstrate DNA is the molecule to pass on traits
Known: Cells release a molecule that can be picked up by other cells
Unknown: Is it DNA or protein?
Experimental organism:
Conclusion:
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Matthew Meselson and Franklin Stahl demonstrated semiconservative replication.
Known: Cells copy their DNA
Unknown: Is it copied conservatively or semiconservatively?
Predicted results after centrifuge
Conservative
Semiconservative
(1 old, 1 new strand)
(2 strands half old/new)
You are provided with an actively dividing culture of E. coli bacteria to which radioactive
adenine has been added. What would happen if a cell replicates once in the presence of this
radioactive base?
A. One of the daughter cells, but not the other, would have radioactive DNA
B. Radioactive adenine would pair with nonradioactive guanine
C. DNA in both daughter cells would be radioactive
Phage grown in radioactive ____________________ were used to infect a culture of bacteria.
Which of the following could be true?
A. Phage DNA was radioactive
B. Phage contained radioactive bacterial proteins
C. Phage coat proteins were radioactive.
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Retroviruses contain RNA instead of DNA. If a virus infects a host cell, it injects its RNA which is
reverse transcribed into DNA. The host cell then transcribes the DNA from the virus into mRNA
and viral proteins are produced. If the retroviruses are grown in a solution with radioactive
__________________________ before infection of the host cell, radioactivity will be found in:
A.
B.
C.
D.
Viral RNA
Host and viral RNA
Host proteins
Viral DNA
What is the DNA sequence of the new strand that will be made to bind to this strand?
Will it be made from right to left or left to right?
5’ AAGTCAGCATAA 3’
A new DNA strand elongates only in the ____________________direction because:
A. DNA polymerase begins adding nucleotides at the 5’ end of the template
B. The phosphate group of the new nucleic acid must bind to a sugar molecule.
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