What is a zygote?

A zygote is defined as a cell that forms when two gametes—specifically, a sperm cell from the male and an egg cell from the female—fuse together during fertilization. This fusion creates a diploid cell, which contains a complete set of chromosomes: half contributed by the sperm and half by the egg. This combination of genetic material marks the beginning of a new organism's development, as the zygote undergoes multiple rounds of cell division and differentiation to eventually form all the tissues and organs of the organism.

The other options do not accurately describe a zygote. A haploid cell, for instance, has only one set of chromosomes, which applies to gametes rather than the fertilized zygote. The mention of a type of gene does not relate to the zygote itself, as genes are segments of DNA housed within chromosomes and are not standalone entities like a zygote. Lastly, the idea of a part of a chromosome also does not pertain to what a zygote is; instead, it is a fully formed cell resulting from the combination of genetic material, rather than a component of a chromosome. Thus, the correct choice that encapsulates the essence of a zygote is that