Because you will focus past ("overshoot") your specimen. (Like using a race car as a shopping cart: it's too fast, and you'll fly past the cereal and never even see it before you realize you need to stop.) Also: you risk crushing the slide and objective against each other (on older or cheaper scopes), and that would be a costly (and embarrassing) mistake.
Answer:
A scientific law is simply an observation of the phenomenon that the theory attempts to explain. For example, suppose that you were lying under an apple tree and observed an apple fall from a branch to the ground. The observation of this phenomena can be called the law of gravity.
Explanation:
Meiosis produces haploid gametes (ova or sperm) that contain one set of 23 chromosomes. When two gametes (an egg and a sperm) fuse, the resulting zygote is once again diploid, with the mother and father each contributing 23 chromosomes.