Teddies Talks Biology - Fourth Edition

Twins Robin and Guy Wheeler - Shells

The two types of twins are Monozygotic and Dizygotic twins which are more commonly known as identical and fraternal twins. The most obvi- ous differences are that identical twins look iden- tical and are the same gender, hence the name, and fraternal twins can look similar or different, the same way that siblings can look similar of dif- ferent, and they can be different genders. Identical twins, or monozygotic twins, are very rare, roughly there are only 3 in every 1000 preg- nancies. No one knows why the zygote splits so most believe it is just an accident during the early stages of pregnancy. Due to the monozygotic twins being from the same fertilised egg cell they have the same DNA hence why twins look the same. Identical twins form very early in the process of pregnancy when the zygote is still just a cluster of cells. When twins split from one fertilised egg this is called monozygotic. There are also dizy- gotic twins which are commonly known as frater- nal twins and occurs naturally due to the female releasing two eggs and the male’s sperm cells fertilising both eggs. Having monozygotic twins is not hereditary alt- hough having dizygotic twins can be hereditary for the gene which means the female releases two egg cells instead of one can be passed on. After birth twins can sometimes develop a lan- guage of their own. This phenomenon is called cryptophasia and both dizygotic twins and monozygotic twins can develop this due to their constant interaction. In ancient times twins were seen as magical for there was no explanation as to why or how twins

occurred. This led to many myths being made up as to whether twins were lucky or unlucky, good or bad. For instance, the Dakota-Indians in North America saw twins as a sign of good luck and they believed that twins came from a special place called twin land and were shown a lot of respect. However, many cultures believed that twins were evil for instance the native South- Americans, the Ainu (the natives of Sakhilan), in old Peru and in the middle ages if a woman gave birth to twins it was bad and either one or both twins died or the twins were killed and the par- ents punished.

Issue 4 | Teddies Talks Biology

15