Black and white twins are called mixed twins.
Understanding Mixed Twins
Mixed twins, also known as biracial twins, occur when fraternal (dizygotic) twins are born to parents of different racial backgrounds, resulting in the twins having noticeably different skin tones and other racial traits. This is a natural occurrence because fraternal twins develop from two separate eggs fertilized by two different sperm, thus inheriting different combinations of genes from their parents.
Key Aspects of Mixed Twins:
- Fraternal Twins: These twins develop from separate eggs and sperm, leading to greater genetic variation between them compared to identical twins.
- Biracial Parents: The genetic differences are often more pronounced when the parents have different racial backgrounds.
- Skin Color Variation: Differences in skin color are a common, yet not the only, visible difference in mixed twins.
- Not Surprising Biologically: The difference in traits are expected due to the diversity of genes present from the two parents.
Examples of Differences in Mixed Twins
Here's a simple breakdown of how differences can appear in mixed twins:
| Trait | Twin 1 | Twin 2 |
|---|---|---|
| Skin Color | Darker | Lighter |
| Hair Texture | Curly | Straight |
| Facial Features | Can differ based on inherited genes | Can differ based on inherited genes |
Biological Explanation
The genetic differences that lead to mixed twins are not unusual. Because fraternal twins are essentially like regular siblings born at the same time, they inherit different sets of genes from their parents. When parents of different racial backgrounds contribute their DNA, these differences in inherited genes can result in significant variations in appearance, particularly in skin pigmentation.
