Biochemistry : DNases

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #1 : D Nases

Which of the following statements about restriction enzymes is true?

Possible Answers:

None of these answers is true

Reverse transcriptase is a DNA polymerase which creates new strands from 3’ to 5’

Restriction enzymes act at RNA mutation sites, to create a covalent bond which links two adjacent exons after an intron sequence is excised

Restriction enzymes can only cut bacterial DNA

Restriction enzymes are endonucleases which recognize a restriction site and cut DNA within or around this site

Correct answer:

Restriction enzymes are endonucleases which recognize a restriction site and cut DNA within or around this site

Explanation:

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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