1 James Watson and Francis Crick discovered the double helix in 1953. 2  In 2003, scientists completed the Human Genome Project.  DNA today can tell us everything from paternity to risk factors for chronic disease.
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. Embryogenesis covers the first eight weeks of development and at the beginning of the ninth week the embryo is termed a fetus.Human embryology is the study of this development during the first eight weeks after fertilisation. The normal period of gestation (pregnancy) is nine months or 38 weeks.n comparison to the embryo, the fetus has more recognizable external features, and a more complete set of developing organs. The entire process of embryogenesis involves coordinated spatial and temporal changes in gene expression, cell growth and cellular differentiation.
The initial stages of human embryogenesis. Human embryogenesis is the process of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, human development entails growth from a one celled zygote to an adult human being.n comparison to the embryo, the fetus has more recognizable external features, and a more complete set of developing organs. The entire process of embryogenesis involves coordinated spatial and temporal changes in gene expression, cell growth and cellular differentiation.