The correct answer is b. halving of chromosomes during gamete formation.
Explanation:
In sexual reproduction, the process of meiosis ensures that each gamete (sperm or egg) receives only half the number of chromosomes as the parent cell. This halving of chromosomes is crucial for maintaining a constant chromosome number in offspring. When a sperm and egg fuse during fertilization, the resulting zygote has the diploid chromosome number (the same as the parent cells), restoring the original chromosome count.
Why other options are incorrect:
a. doubling of chromosomes after zygote formation:
The zygote is formed when two haploid gametes (sperm and egg) fuse, resulting in a diploid cell with the same number of chromosomes as the parent. There is no doubling of chromosomes after zygote formation.
c. doubling of chromosomes after gamete formation:
There is no doubling of chromosomes after gamete formation. Meiosis, the process of gamete formation, specifically halves the chromosome number.
d. halving of chromosomes after gamete formation:
While technically correct, “halving of chromosomes after gamete formation” is a more precise description of the process. The halving occurs during gamete formation through meiosis.