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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$I.$ Flippers of whale and wings of bat exhibit analogy.
$II.$ Wings of butterfly and wings of bird exhibit homology.
$III.$ Organs with dissimilar structure are called analogous organs.
$IV.$ Organs with similar structure and origin are called homologous organs.
$I. X-ray$ film
$II.$ Electrophoresis
$III.$ Digestion with restriction enzyme
$IV.$ Ethidium bromide
$V.$ Radioactive probe
Choose the option having correct sequential order of these events