Multiple choice

Which of the following terminologies is not correctly defined?

  1. Restriction endonuclease: An enzyme responsible for restricting the growth of bacteriophage in Escherichia coli by the addition of methyl groups to DNA.

  2. Cytogenetics: Study that relates appearance and behaviour of chromosomes to genetic phenomenon.

  3. Commensalism: A close association of two or more dissimilar organisms.

  4. Palindromic DNA: A sequence of base pairs that reads same on the two strands when orientation of reading is kept the same.

  5. Dideoxynucleotides: A deoxynucleotide that is used in DNA sequencing and the treatment of viral diseases.

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A Correct answer
Explanation

In the year 1963, the two enzymes, restriction exonuclease and restriction endonuclease, responsible for restricting the growth of bacteriophage in Escherichia coli were isolated. One of these enzyme (exonuclease) added methyl groups to DNA, while the other cut DNA (endonuclease). Restriction exonuclease removes nucleotides from the ends of the DNA, whereas restriction endonuclease makes cuttings at specific positions within the DNA.

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