<span>Only one sperm normally fuses
with an egg because if more than one sperm fuses, through a process
called polyspermy, development of the zygote usually stops.
</span>
<span>Fertilization of one egg by
two sperm is possible, but the resulting zygote is almost never viable
because such a zygote would have three sets of chromosomes instead of
the normal two. This condition, called triploidy, is usually
incompatible with life. Those rare triploid infants that do survive to
term have severe and multiple birth defects and rarely live more than a
few days. </span>
Chromosomes exchange genetic material in step 3.
<h3><u>Explanation</u>:</h3>
The meiosis is the type of cell division that takes place for gametogenesis. The meiosis has two phases - meiosis I and meiosis II.
The meiosis I has the events like crossing over and independent assortment which leads to the mixing of genes between homologous chromosome pairs and separation of homologous chromosome pairs. So the two cells that are produced from the meiosis I are genetically different. The step 3 shows the crossing over of prophase 1 of meiosis I. So, it shows the genetic difference between the offsprings and leads to genetic variation.
The answer is a hope it helps
