MCQ
Purines possess nitrogen at which position?
- A1, 2, 4 and 6 position
- B1, 3, 5 and 7 position
- C1, 3, 7 and 9 position
- D1, 2, 6 and 8 position
Explanation:
Purines consist of a six-membered and a five-membered nitrogen containing ring, fused together. It possesses nitrogen at 1,3,7 and 9th position.

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$I.$ Eco. $RI$ restriction endonuclease enzyme is isolated from Escherichia coli $RY13$
$II.$ Its recognition sequence is $5^{\prime}-$ $GAATTC - 3 '$
$3^{\prime}-C T T A A G-5^{\prime}$
$5^{\prime}-G-A-A-T-T-C-3^{\prime}$
$3^{\prime}-C-T-T-A-A-G-5^{\prime}$
$III.$ Its site of cleavage is