The diagram given below represents a stage during cell division. Study the same and answer the questions that follow: The diagram given below represents a stage during cell division. Study the same and answer the questions that follow:
Name the type of cell division that occurs during: 1. Replacement of old leaves by new ones. 2. Formation of gametes.
Topic: Mitosis and meiosis
Answer
- Replacement of old leaves by new ones — MITOSIS
- Formation of gametes — MEIOSIS
THE RULE that decides every such question: MITOSIS for GROWTH AND REPAIR of body cells; MEIOSIS ONLY for the formation of GAMETES.
MITOSIS — number of chromosomes UNCHANGED (46 → 46); TWO daughter cells, genetically IDENTICAL to the parent. That is exactly what growing new leaves requires.
MEIOSIS — number HALVED (46 → 23); FOUR daughter cells, NOT identical. Necessary so that fertilisation restores the full number rather than doubling it each generation.
Meiosis also produces VARIATION, through crossing over and the independent assortment of chromosomes — which is why siblings differ from one another.