How is the chromosome number maintained from one generation to another in sexually reproducing organisms?

Correct option is C

Sol: The correct answer is (c) Halving of chromosomes during gamete formation

Key points:

• In sexually reproducing organisms, the chromosome number is maintained from one generation to the next through a process called meiosis. During meiosis, the chromosome number is halved in the gametes (sperm and egg cells) so that each gamete contains half the number of chromosomes of a somatic (body) cell. This is known as the haploid number (n).
• ​When fertilization occurs, the sperm and egg combine to form a zygote, restoring the diploid number (2n) of chromosomes. This ensures that the offspring has the same number of chromosomes as the parents. Here’s how it works:

• (I) Meiosis: The gametes undergo meiosis, which reduces the chromosome number by half (haploid).
• (II) Fertilization: The haploid sperm and haploid egg fuse during fertilization, resulting in a zygote with the diploid number of chromosomes.

• By halving the chromosome number during gamete formation, sexually reproducing organisms maintain a consistent chromosome number across generations.

All other option:

•  Doubling of chromosomes during gamete formation
  If chromosomes doubled during gamete formation, gametes would end up with twice the number of chromosomes, leading to a zygote with an excessively high chromosome count after fertilization. This would disrupt genetic stability.
• Doubling of chromosomes during zygote formation
  Doubling chromosomes during zygote formation doesn't occur. The zygote forms by the fusion of two haploid gametes, restoring the diploid chromosome number. Doubling chromosomes at this stage would again lead to an abnormal chromosome number.
  
•  Halving of chromosomes during zygote formation  
  Halving chromosomes during zygote formation would be counterproductive, as the zygote needs to have a full set (diploid) of chromosomes to develop into a healthy organism. This option doesn't align with biological processes.