Restriction enzymes were first discovered with the observation that
a. DNA is restricted to the nucleus.
b. bacteriophage DNA is destroyed in a host cell.
c. foreign DNA is kept out of a cell.
d. foreign DNA is restricted to the cytoplasm.
e. all of the above

Verified step by step guidance

1. Understand the role of restriction enzymes in bacterial cells.
2. Recognize that restriction enzymes are part of a bacterial defense mechanism against bacteriophages.
3. Consider how bacteriophages, which are viruses that infect bacteria, introduce their DNA into the host bacterial cell.
4. Identify that the bacterial cell uses restriction enzymes to cut and destroy the invading bacteriophage DNA.
5. Conclude that the discovery of restriction enzymes was linked to the observation of bacteriophage DNA being destroyed in a host cell.

Key Concepts

Restriction Enzymes

Restriction enzymes, also known as restriction endonucleases, are proteins produced by bacteria that can cut DNA at specific sequences. They serve as a defense mechanism against foreign DNA, such as that from bacteriophages, by recognizing and cleaving it. This ability to cut DNA has made them invaluable tools in molecular biology for cloning and genetic engineering.

Bacteriophage Interaction

Bacteriophages are viruses that infect bacteria, and their DNA can be recognized as foreign by bacterial cells. When a bacteriophage injects its DNA into a bacterial host, the restriction enzymes can target and degrade this foreign DNA, preventing the virus from hijacking the bacterial machinery for replication. This interaction highlights the role of restriction enzymes in bacterial immunity.

Foreign DNA Recognition

The recognition of foreign DNA is crucial for the function of restriction enzymes. Bacteria have evolved mechanisms to distinguish between their own DNA and that of invading entities, such as viruses or plasmids. This selective recognition allows restriction enzymes to protect the bacterial genome while enabling the incorporation of beneficial genetic material through processes like horizontal gene transfer.