Question

what is the main cause of variations among organisms during sexual reproduction ?

Answer 1

The variations in organisms is due to the variations in the Gene of every organism

Answer 2

Could the answer by mutations in DNA?

Answer 3

If @bediprabhjot is referencing sexual reproduction, he/she may be looking for 1) chromosome "crossing over" and 2) metaphase and the aligning of chromosomes. I may also agree with Vintage, mutations can also be a very common form of genetic variation.

Answer 4

Aside from mutation the sexually reproducing variation is due to independent orientation of chromosomes in meiosis ( two ways the sister chromatids can line up in their tetrads ), crossing over ( non-sister chromatids exchanging sections of genetic material ) and random fertilization in which male and female gametes randomly come together to form zygotes.

Answer 5

Since the DNA is a mixture of two parents, the offspring obviously is different from the parents. If you're talking about mutation, then that's when the DNA doesn't quite split right and the offspring has one less or one more chromosome.