Define zygote.

Hint: The cell formed by the union of a male reproductive cell (a sperm) and a female reproductive cell (an ovum). The zygote develops into the embryo. The unification of a sperm and an ovum to make a zygote constitutes fertilization. The zygote's genome is a combination of the DNA of both the gametes. Each gamete contains all of the genetic information necessary to form a new individual.

Complete answer:
A zygote is a fertilized ovum. The germ cells undergo meiosis, to be in a haploid state (n) as a part of spermatogenesis and oogenesis. The sperm and therefore the unfertilized ovum reinstates a chromosome set in zygote during a diploid state (2n).

The cellular mechanisms present within the gametes also function within the zygote, but the newly fused DNA produces a different effect in the new cell. In single-celled organisms, the zygote becomes a totally functioning organism and may divide through mitosis to produce offspring. The organism also can produce gametes to reproduce sexually with other cells.

The zygote represents the primary stage in the development of a genetically unique organism. The joining of haploid gametes to form a diploid zygote may be a common feature within the sexual reproduction of all organisms except bacteria.

The zygote contains all the essential factors for development, but they exist solely as an encoded set of instructions localized within the genes of chromosomes. The genes of the new zygote aren't activated to produce proteins until several cell divisions into cleavage. During cleavage, the zygote directly subdivides into many smaller cells of conventional size through mitosis. These smaller cells are called blastomeres.

In most animals, the gamete cells are converted to haploid cells before reproduction, in a process known as meiosis. By reducing the number of alleles in each gene to 1, a zygote formed by two haploid gametes will have the proper number of alleles.

Note: A zygote is defined as a eukaryotic cell formed by a fertilization event between two gametes. In the resulting zygote, the DNA material from the two cells is combined.
The cells from each parent that combine to make the zygote are called gametes. In humans, the male gamete is named sperm, and therefore the female gamete has named an egg. When the gametes fuse they form a cell called a zygote. In plants, the fusion of the female ovule and therefore the male sperm develops a zygote.