Restriction endonucleases are the enzymes
Ans. b (They cleave the DNA at specific sequence) (Ref. Harper's Illustrated Biochemistry, 26lh/57, 397; Table 40-2)RESTRICTION ENDONUCLEASES# Restriction enzyme: An endodeoxynuclease that causes cleavage of both strands of DNA at highly specific sites dictated by the base sequence.# The detection of restriction fragment length polymorphisms (RFLPs) facilitates prenatal detection of hereditary disorders such as:- Sickle cell trait,- Beta thalassemia,- phenylketonuria, and- Huntington's disease.# Detection of RFLPs involves cleavage of double-stranded DNA by restriction endonucleases, which can detect subtle alterations in DNA that affect their recognized sites.Enzymes capable of degrading nucleic acids (nucleases) can be classified in several ways:# Those which exhibit specificity for deoxyribonucleic acid are referred to as deoxyribonucleases.# Those which specifically hydrolyze ribonucleic acids are ribonucleases.# Within both of these classes are enzymes capable of cleaving internal phosphodiester bonds to produce either 3'- hydroxyl and 5'-phosphoryl terminals or 5'-hydroxyl and 3'-phosphoryl terminals. These are referred to as endonucleases.# There exist classes of endonucleases that recognize specific sequences in DNA; the majority of these are the restriction endonucleases, which have in recent years become important tools in molecular genetics and medical sciences.# Some nucleases are capable of hydrolyzing a nucleotide only when it is present at a terminal of a molecule; these are referred to as exonucleases.- Exonucleases act in one direction (3-5 or 5-3) only. In bacteria, a 3-5 exonuclease is an integral part of the DNA replication machinery and there serves to edit--or proofread--the most recently added deoxynucleotide for base- pairing errors.Educational points:# Restriction enzymes cut DNA of any source into short pieces in a sequence-specific manner--in contrast to most other enzymatic, chemical, or physical methods, which break DNA randomly.# Restriction enzymes & DNA ligase are also used to prepare chimeric DNA molecules.
Used for joining DNA to vector
They cleave the DNA at specific sequence
They cleave the DNA randomly
Diagnoses DNA molecule from diseases
Molecular Genetics