Yes, cousins do share DNA.
How Cousins Share DNA
Cousins share DNA because they inherited it from the same ancestors. Specifically, first cousins share DNA inherited from their mutual grandparents. This means that some of the DNA present in a grandparent is passed down to their children (the parents of the cousins) and then passed down again to their grandchildren (the cousins themselves). The shared DNA indicates a genetic connection and relationship between the cousins.
The Amount of Shared DNA
The amount of DNA shared between cousins varies. First cousins, on average, share about 12.5% of their DNA. This is because the shared DNA goes through two rounds of inheritance, decreasing by approximately half each time. This percentage can vary depending on which specific genes are inherited from each parent.
Here's a simplified breakdown:
| Relationship | Shared DNA (Approximate) |
|---|---|
| Siblings | 50% |
| Parent-Child | 50% |
| First Cousins | 12.5% |
Practical Implications
- Genetic Testing: DNA testing can reveal the percentage of shared DNA between relatives. This can be used to confirm family relationships.
- Understanding Traits: Shared DNA is the reason why cousins may share some similar physical traits or have a predisposition to similar health conditions. This is because the DNA that controls these traits and conditions is passed down through the family.
Summary
In conclusion, cousins definitely share DNA because they have ancestors in common. The shared DNA is inherited from their common grandparents and contributes to their genetic relatedness.
