Final answer:
Restriction endonucleases make specific cuts within the DNA molecule at specific nucleotide sequences, generating blunt or sticky ends utilized in recombinant DNA technology.
Step-by-step explanation:
Restriction endonucleases (or restriction enzymes) are enzymes that make cuts at a specific position within the DNA molecule. These specialized enzymes are highly specific, recognizing unique DNA sequences, often palindromic, to cleave the phosphodiester bonds that hold the DNA strands together. They were initially discovered as part of a bacterial defense mechanism against bacteriophages. Over 800 types of restriction endonucleases are known, with each typically recognizing different DNA sequences and cutting at those precise sites. For example, the restriction enzyme EcoRI recognizes the sequence 5'GAATTC3' and cuts between G and A on both strands of DNA. These cuts can result in 'blunt' or 'sticky' ends, depending on how the enzyme cleaves the DNA. Sticky ends are single-stranded overhangs that can hydrogen bond with complementary sequences on other DNA fragments, facilitating the ligation process in the creation of recombinant DNA.