AIPMT 2003 question paper with solutions

1. Recall the concept of the quiescent centre: Proposed by Clowes in 1961, the quiescent centre refers to a group of cells located within the root apical meristem that show very slow or no cell division, unlike the actively dividing cells around them.

2. Recall the biochemical characteristics of these cells: Because these cells are not actively dividing, they have a comparatively lower concentration of DNA, RNA, and protein than the surrounding actively dividing meristematic cells.

3. Connect this to their appearance: This lower biochemical activity is reflected in their appearance — they show light (less dense) cytoplasm and small nuclei, in contrast to actively dividing cells which typically show dense cytoplasm and prominent nuclei.

4. Eliminate the other options: Tunica and corpus are concepts related to the shoot apical meristem's zonation (not the root's quiescent centre), and the quiescent centre cells do not divide regularly — they are largely inactive.

Hence, the cells of the quiescent centre are characterised by having light cytoplasm and small nuclei, so the answer is A.

1. Recall the dominant/recessive relationships Mendel established for each trait. For seed colour, yellow was dominant over green; for pod colour, green was dominant over yellow; for flower position, axial was dominant over terminal; and for seed shape, round was dominant over wrinkled.

2. Check option A, Green seed colour. Since yellow is dominant and green is recessive for seed colour, this is indeed a recessive feature.

3. Check option B, Green pod colour. Since green pod colour is actually the dominant trait (with yellow being recessive) for this particular character, this is not recessive.

4. Check option C, Axial flower position. Since axial position is the dominant trait for flower position, this is not recessive.

5. Check option D, Round seed shape. Since round shape is the dominant trait for seed shape, this is not recessive.

Hence, the correct answer is Option A, Green seed colour.

1. Recalling the organizational level of sponges: Sycon is a sponge, and sponges are considered the simplest multicellular animals, showing what is called a cellular level of organization — meaning their cells work somewhat independently rather than being organized into true tissues.

2. Checking option A (unicellular): Sponges are clearly multicellular, made up of many cells, so this option is incorrect.

3. Checking option C (gastrovascular system): A gastrovascular cavity is a feature of cnidarians (like Hydra), not sponges, which instead have a unique water canal system.

4. Checking option D (tissue organization, no body cavity): This describes organisms like flatworms that have progressed to true tissue-level organization, which is more advanced than the simple cellular level seen in sponges.

5. Checking option B (multicellular without tissue organization): This correctly captures the sponge's cellular grade of organization, where cells are loosely associated without forming true, coordinated tissues.

6. Conclusion: Sycon, being a sponge, is best described as multicellular without tissue organization. Hence, the answer is option B.