Question

Mention the number of chromosomes at each stage. Correlate the life phases of the individual with the stages of the process.

Hint:

In oogenesis, meiosis is incomplete until fertilization. This ensures that the female gamete (ovum) is haploid, ready to merge with the male gamete during fertilization. In pollination, the main aim is to transfer pollen efficiently between flowers to ensure genetic diversity.

Answer 1

Chromosome number at each stage:
- Oogonium (2n): The chromosome number is diploid (46 chromosomes in humans).
- Primary oocyte (2n): Still diploid (46 chromosomes), but the cell is arrested in prophase I of meiosis.
- Secondary oocyte (n): Haploid (23 chromosomes). The primary oocyte undergoes meiosis I to form one secondary oocyte and one polar body.
- Mature ovum (n): Haploid (23 chromosomes). It completes meiosis II upon fertilization.
Life Phases and Oogenesis Stages:
- Pre-puberty: Oogonia undergo mitosis.
- At puberty: Primary oocytes begin meiosis I but arrest in prophase I until ovulation.
- During ovulation: A secondary oocyte is released.
- Fertilization: The secondary oocyte completes meiosis II to form the mature ovum.