Final answer:
The normal role of restriction enzymes in bacteria is to defend against foreign DNA by recognizing and cleaving specific sequences, often palindromic. Bacteria protect their own DNA from these enzymes through methylation via the restriction modification system. These enzymes are also critical tools in recombinant DNA technology.
Step-by-step explanation:
Role of Restriction Enzymes in Bacteria
The normal role of restriction enzymes in bacteria is to protect them from invading foreign DNA, such as that of bacteriophages (viruses that infect bacteria). These enzymes recognize specific DNA sequences, which are often palindromic, and cleave the DNA at these sites, thereby 'restricting' the invasion of the foreign DNA and preventing infection.
Bacterial Protection Against Restriction Enzymes
Bacteria protect their own DNA from restriction enzymes through a system called the restriction modification system. This system involves the modification of the bacterial DNA by a type of enzyme known as DNA methylase, which adds methyl groups to the bases within the recognition sequences. As a result, the restriction enzymes do not recognize or cut the methylated DNA, ensuring that the bacteria's own DNA remains intact.
Diversity of Restriction Enzymes
There are over 800 discovered restriction endonucleases, each with the ability to recognize different specific sequences in the DNA. These enzymes have been pivotal in the development of recombinant DNA technology, allowing scientists to cut DNA at specific sites and create recombinant molecules for various applications in genetic engineering.