tools of biotechnology
Molecular biologists use tools to altering the gentic makeup of organisms. The tools of the molecular biologist are living biological organisms or biological molecules. The tools can be used to cut, join, and replicate DNA by treating specific DNA sequences as modules and move them from one DNA molecule to another, forming recombinant DNA.
Restriction endonucleases (RE) & recognition sites
Also known as restriction enzymes, that act as molecular scissors that cleave double-stranded DNA into fragments at a specific base-pair sequence. These specific sequence of nucleotides are known as the recognition site and can make a precision cut. Most recognition sites are four to eight base pairs long and are characterized by palindromic sequences (sequences that are the same when read from the 5' and 3' end)
The ends of the DNA fragments produced differ according to the different RE. The ends produced depend on the where the phosphodiester bonds are broken in the recognition site.
Stikcy ends (top image): fragment end of a DNA molecule with short single-stranded overhangs Blunt ends (bottom image): fragment ends of a DNA molecule that are fully base-paired. |
methylases
It is a type of an enzyme that adds a methyl group to one of the nucleotides found in a restriction enzyme’s recognition site. This process is important for an organism to differentiate between its own DNA and foreign DNA.
• Foreign DNA is not methylated and is therefore cleaved
• Plays an important role in protecting a gene fragment from being cleaved at the wrong location
(protects bacterium’s own DNA)
• Found both in prokaryotes and eukaryotes
• Foreign DNA is not methylated and is therefore cleaved
• Plays an important role in protecting a gene fragment from being cleaved at the wrong location
(protects bacterium’s own DNA)
• Found both in prokaryotes and eukaryotes