Final answer:
Restriction enzymes are enzymes that precisely cut DNA at specific palindromic sequences, which are the same in both directions. They can produce 'sticky ends' or 'blunt ends' and are essential tools in molecular biology and genetic engineering.
Step-by-step explanation:
Restriction enzymes, also known as restriction endonucleases, are enzymes that recognize and cleave DNA at specific sequence motifs. These motifs are typically palindromic sequences, meaning the sequence of nucleotides reads the same in the 5' to 3' direction on one strand as it does in the 5' to 3' direction on the complementary strand. Type II restriction endonucleases, for example, EcoRI, cut the DNA at precise locations within these recognition sequences, often producing overhangs known as 'sticky ends' or a straight cut producing 'blunt ends.' These enzymes are highly specific, favoring their cognate DNA sequence million-fold over other sequences.
The recognition patterns for restriction enzymes generally contain four to six base pairs and have a symmetric nature which complements the twofold symmetry of the enzymes, which are usually dimers. This specificity allows for the use of restriction enzymes in various molecular biology applications such as DNA fingerprinting, genetic engineering, and recombinant DNA technology. By exploiting the natural defense mechanism of bacteria against viruses, scientists can cut DNA at predictable sites to create recombinant molecules essential for research and biotechnology.
To illustrate, the restriction endonuclease EcoRI recognizes the sequence 5'GAATTC3' and cuts the DNA between G and A, leaving 'sticky ends'. These can be paired with complementary DNA fragments cut by the same enzyme to form recombinant DNA sequences. Thus, by precisely cleaving DNA at specific sites, restriction enzymes serve as invaluable tools in genetic engineering and diagnostic research.