Search results
Results from the WOW.Com Content Network
The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula. The morula develops into a structure called a blastula through a process called blastulation. The blastula develops into a structure called a gastrula through a process called gastrulation.
The zygote is the earliest developmental stage. In humans and most other anisogamous organisms, a zygote is formed when an egg cell and sperm cell come together to create a new unique organism. The formation of a totipotent zygote with the potential to produce a whole organism depends on epigenetic reprogramming.
The genetic material of the sperm and egg then combine to form the single cell zygote and the germinal stage of development commences. Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages .
In biological terms, human development entails growth from a one-celled zygote to an adult human being. Fertilization occurs when the sperm cell successfully enters and fuses with an egg cell . [2] The genetic material of the sperm and egg then combine to form a single cell called a zygote and the germinal stage of prenatal development commences.
The DNA from the ovule and pollen combine to form a diploid, single-cell zygote that will develop into an embryo. [21] The zygote, which will divide multiple times as it progresses throughout embryonic development, is one part of a seed.
As the zygote undergoes cell division to form two, then four, then eight and then 16 cells (typically by day four after fertilization), it becomes a ball of cells called a morula. During these cellular divisions, the zygote remains the same size, but the number of cells increase.
The zygote will develop into a male if the egg is fertilized by a sperm that carries a Y chromosome, or a female if the sperm carries an X chromosome. [5] The Y chromosome contains a gene, SRY, which will switch on androgen production at a later stage leading to the development of a male body type.
The division of blastomeres from the zygote allows a single fertile cell to continue to cleave and differentiate until a blastocyst forms. The differentiation of the blastomere allows for the development of two distinct cell populations: the inner cell mass, which becomes the precursor to the embryo, and the trophectoderm, which becomes the precursor to the placenta.