What Makes a Twin a Twin?

  • By: Maya
  • Date: March 31, 2022
  • Time to read: 3 min.

Twins are two babies who were born at the same time, usually within a few minutes of each other. Twins share all of the same genetic information, so they have identical DNA and are considered as one individual. Twins can be either fraternal or identical. Fraternal twins happen when two eggs are fertilized by two different sperm and result in two babies who look very different from each other. Identical twins happen when both eggs are fertilized by the same sperm and result in babies who have the same exact genetic information.

Twins and Genetics: What makes a twin a twin?

Twins are special because they come from the same egg and sperm. This means that they have the exact same genetic information. Twins share 100% of their DNA, which is why they are so similar. Twins also share many personality traits and often have very close relationships. It is not clear why twins happen, but there are some things that can increase your chance of having twins. Some factors that can increase your chances of having twins include: fertility problems, being over 30 years old, having two low birth weight babies, being obese before you were pregnant, and carrying a gene for twinning.

Identical Twins: How are they made?

Identical twins are made when one fertilized egg splits into two and each becomes a separate individual. The process is called gastrulation. However, the timing of this event and what causes it are still unknown. It’s possible that two eggs join at the same spot but there is no real evidence to support this theory. There are several theories about what makes twins identical including genetic similarity, exposure to the same hormones during development, and even some sort of magical intervention.

Fraternal Twins: What causes them?

Twinning is a rare event where two fertilized eggs are implanted in the uterus at exactly the same time. Identical twins, who share all of their genetic material, are the most common type of twin. However, there are also fraternal twins- siblings who have different genetic contributions. What makes twins a twin? Twins share 100% of their DNA, which is why they are genetically so similar. Fraternal twins can share up to 50% of their DNA, but still be considered twins because they share enough unique genetic information to identify them as such. There are several factors that can contribute to twinning, but one of the most common is fertility problems that lead to multiple eggs being released during ovulation. If two or more eggs are released and implant in the uterus, then these will become twins.


In conclusion, identical twins are formed when a fertilized egg splits in two. This happens very early in the pregnancy, sometimes before the woman even knows she is pregnant. However, not all twins are identical. Fraternal twins are formed when two eggs are fertilized by two different sperm cells. This can happen either at the same time or a few days apart. There is no real way to tell if twins are identical or fraternal until they are born.

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