Chapter 12 DNA Review Part 1

During the 20th century, scientists were determined to?

They were determined to discover which part of a cell held the genetic material.

In 1928, Griffith was attempting to?

He was attempting to develop a vaccine against Streptococcus pneumoniae.

Streptococcus bacteria exists as two types. What are these two types?

These two types are S strain bacteria (smooth and harmful colonies) and R strain bacteria (rough and harmless colonies).

What happened when Griffith injected the S strain (harmful) bacteria into a mouse?

When Griffith injected the S strain bacteria into a mouse, that mouse died.

What happened when Griffith injected the R strain (harmless) bacteria into a mouse?

When Griffith injected the R strain bacteria into a mouse, that mouse lived.

What happened when Griffith injected the dead S strain bacteria into a mouse?

When Griffith injected the dead S strain bacteria into a mouse, that mouse lived.

What happened when Griffith injected the dead S strain bacteria combined with the dead R strain bacteria into a mouse?

When Griffith injected the dead S strain bacteria combined with the dead R strain bacteria into a mouse, that mouse died.

What were Griffith's conclusions after his experiments?

His conclusions were that genetic material must have passed from the dead S strain bacteria to the living R strain, transforming the R strain to be harmful.

What did Griffith's conclusions lead investigators to start?

They led investigators to start experiments to find out what part of the cell was the transforming substance/genetic material.

What was the purpose of Avery's experiments?

The purpose was to determine the part of the heat-killed S strain bacteria that caused transformation.

What was the procedure of Avery's experiment?

The procedure was that Avery treated the heat-killed S strain bacteria with enzymes that destroyed proteins, lipids, carbohydrates, and RNA.

Did transformation occur during Avery's experiment?

Yes, transformation still occurred, even if people at the time believed that proteins were most likely what genes were made of.

What was the conclusion of Avery's experiment?

The conclusion was that none of those cell components were the genetic material that was getting transferred from one bacteria cell to another.

What happened when Avery's team repeated Avery's experiment using enzymes that would break down DNA in the bacteria?

When they repeated his experiment using these enzymes, transformation did not occur. Therefore, DNA was the transforming factor/genetic material.

What is the summary of Avery's experiment?

The summary of Avery's experiment is that since DNAase destroyed DNA in the S strain, it could not transfer DNA to the R strain. This proved that DNA is the genetic material, because in the other experiments the parts of the cell that were not the genetic material (proteins, lipids, RNA) were destroyed leaving DNA (which is the genetic material) able to pass to the R strain and make it harmful.

Alfred Hershey and Martha Chase performed an experiment to?

They performed an experiment to verify Avery's discovery.

Hershey and Chase studied what?

They studied viruses, particularly bacteriophages.

What are viruses?

They are nonliving particles that can infect living cells that consist only of a protein coat and DNA.

What is a bacteriophage?

It is a virus that infects bacteria.

Bacteriophages inject their genetic material into?

They inject their genetic material into bacterial cells. After doing this, they use the bacteria as a host to make many new viruses.

Hershey and Chase wanted to determine?

They wanted to determine which part of the virus (protein coat or DNA) entered the bacterial cell.

What part of the virus enters the bacterial cell?

The part that enters is the genetic material (DNA).

During Hershey and Chase's experiments, two different bacteriophages (viruses) were tagged using?

They were tagged using radioactive isotopes. One was tagged with P-32 to trace DNA (P-32 is phosphorus) and the other was tagged with radioactive S-35 to trace the protein (S-35 is sulfur).

During Hershey and Chase's experiments, the bacteriophage with P-32 (phosphorus, DNA tracker) injected its genetic material into?

It injected its genetic material into a bacteria cell.

What was the conclusion of Hershey and Chase's experiments?

The conclusion was that most of the P-32 labeled DNA was found in the cells of the bacteria.

What did the results of Hershey and Chase's experiments indicate?

These results indicated that only the DNA (not the protein) of a virus enters the host, where viral reproduction takes place. Therefore, DNA is the genetic material.