What percentage of genes do Dizygotic twins share?

• A. 0%
• B. 25%
• C. 50%
• D. 100%

Answer: (C)

Dizygotic twins, also known as fraternal twins, originate from two separate eggs that are fertilized by two separate sperm cells. Because they come from two distinct zygotes, they share approximately 50% of their genetic material on average. The genetic similarity is comparable to that of siblings who are not twins. This sharing occurs because each twin inherits a mix of genes from both parents, leading to the 50% genetic overlap typical of non-twin siblings.

In contrast to the other options, it's important to note that dizygotic twins do not share 0% of their genes, as they are derived from the same parents and thus inherit some genetic material. They also do not share 25% of their genes, which would be more typical for other relationships like half-siblings, and they certainly do not share 100% of their genes, which is characteristic of monozygotic (identical) twins, who develop from a single fertilized egg that splits into two. Therefore, the shared genetic similarity of about 50% is a key characteristic that distinctly defines the relationship among dizygotic twins.