Frogs go through various developmental stages, some of which will determine the sex of the frog. When frogs first hatch, they are tadpoles that eventually develop into the frogs we see hopping around rivers and lakes.
Fertilization of the Egg
Frog eggs are much larger than a single frog cell when developed. This egg turns into the tadpole that has millions of cells, but the volume from the organism to the tadpole never changes. When the sperm first fertilizes the egg, the sperm and egg become fused together. This creates a diploid zygote nucleus.
Cleavage occurs when the egg starts to develop. It starts where the sperm fused with the egg, and a furrow is created that wraps around the egg. It then divides into two cells. This will all happen in a matter of a day. At the end of it all, a blastula will exist, which is a cavity that is filled with fluid. As soon as there are at least 4,000 cells in the blastula, the genes of the zygote will begin to develop.
Patterning includes another process called gastrulation. During these phases, the tadpole body will begin to form. First the head and tail will take shape, then the back and stomach, and finally the sides will take shape. In gastrulation the zygote genes are dictating what the frog looks like.
During differentiation, the frog embryo develops skin, muscles, blood, tissues, organs and everything else needed to survive. After the organs and body systems have differentiated themselves, the embryo will become a tadpole. Eventually, the tadpole will become a frog and will develop into either a male or a female. This is determined after the frog is in the tadpole stage, not the embryonic stage.