Biochemistry : DNases
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Example Question #161 : Biochemistry
Which of the following statements about restriction enzymes is true?
Restriction enzymes are endonucleases which recognize a restriction site and cut DNA within or around this site
Restriction enzymes act at RNA mutation sites, to create a covalent bond which links two adjacent exons after an intron sequence is excised
None of these answers is true
Restriction enzymes can only cut bacterial DNA
Reverse transcriptase is a DNA polymerase which creates new strands from 3’ to 5’
Restriction enzymes are endonucleases which recognize a restriction site and cut DNA within or around this site
Reverse transcriptase synthesizes DNA in the 5' to 3' direction, using RNA as a template (hence it is the reverse of transcription). Restriction enzymes act only on DNA, not RNA, and they can cut bacterial as well as viral DNA—indeed, they can provide protection against viruses—and are found in archaea. Restriction enzymes can recognize specific sequences of nucleotides at restriction sites and cut DNA at these sites. Restriction enzymes do not create covalent bonds between adjacent exons after intron excision, rather this is done by tRNA splicing ligase.
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