Artificial embryo twinning is a method of making clones that mimics the natural process of creating identical twins, according to the Genetic Science Learning Center. It uses the same approach as natural cloning, but it ... More »

Identical twins have the same DNA code because they are the result of an embryo splitting in half. Fraternal twins do not share the same DNA because they are a result of two separate embryos. More » Science Biology Molecular Biology & DNA

After fertilization, the cells in the zygote divide rapidly to form a morula, which becomes the embryo after approximately five days. The fetus is present about eight weeks after the fertilization takes place. More »

The National Institutes of Health defines therapeutic cloning as cloning an embryo only for the purpose of producing embryonic stem cells with the same DNA as the donor cell. Therapeutic cloning aims to create stem cells... More » Science Biology

The first cows were cloned by separating one cell from a developing cow embryo and, using electricity, fusing it to a donor cell. The cow embryo cell had the nucleus, which contains DNA. When the fused cell started divid... More » Science Biology

Paternal and maternal twins, commonly known as fraternal and identical twins, are distinguished by the different ways the multiple pregnancy begins. Identical twins begin as a single zygote that splits into two or more d... More »

Rarely, a boy and girl may be identical twins. This condition, called Turner Syndrome, afflicts very few pairs of twins. The gender difference occurs when an egg and a sperm pair that begins as two males, loses a copy of... More »