Question

why will each gamete contain only one gene set

Answer 1

Because they Are formed by meiotic type of cell division. This is necessary As the two Types of gametes fuse during sexual reproduction to form zygote

Answer 2

Since gametes from both the parents fuse to form the zygote they need to have only one set.If they had two sets , the numbers of chromosomes in the off spring would go on doubling..and to avoid this gametes have only one set.