Final answer:
Restriction endonucleases, sometimes thought of as 'molecular clamps,' are enzymes found in various bacterial species that cleave DNA at specific sequences. Three main types exist—type-I, type-II, and type-III—with type-II like EcoRI being the most utilized in genetic engineering. EcoRI, derived from E. coli, specifically recognizes and cuts the palindromic sequence 5'GAATTC3', producing 'sticky ends' useful for cloning.
Step-by-step explanation:
Types of DNA Clamps in Organisms
The term 'DNA clamps' is a bit misleading in the context of the information provided, as it usually refers to protein complexes that help DNA polymerase maintain its association with the template strand during replication. However, from the context given, we seem to be discussing restriction endonucleases, which are indeed different from DNA clamps. In light of this, I'll address restriction endonucleases, which can be considered as 'molecular clamps' that detect foreign DNA based on sequence recognition.
There are three types of restriction endonucleases: type-I, type-II, and type-III. Type-II restriction endonucleases, such as EcoRI, are the most widely used in molecular biology due to their precision in cutting DNA at specific recognition sequences. They are found in various bacterial species, with each enzyme recognizing specific, often palindromic, DNA sequences and cutting DNA at or near these sites. The name of each enzyme is derived from the bacterial species from which it is isolated, as indicated by a three-letter abbreviation, followed by a Roman numeral or other characters to distinguish enzymes from the same species but with different recognition sites.
An example is EcoRI, which recognizes the palindromic sequence 5'GAATTC3' by clamping onto the DNA and cleaving between G and A on both strands, leading to staggered cuts that produce 'sticky ends'. These sticky ends are useful in various biotechnology applications, such as cloning DNA fragments into plasmids. Such enzymes are essential tools for genetic engineering and recombinant DNA technology. The extracted DNA, after treatment with these enzymes, is referred to as "restricted DNA" because it has been cut at specific sites.