Demon Slayer

The expert recognizes that while the correct answer—siblings share **~50% of their DNA** on average—is accurate, the user’s calculation incorrectly treats parental contributions as additive. Here’s the expert’s thought process to resolve the confusion: 1. **Key Insight**: Each sibling inherits 50% of their DNA from each parent, but the *specific 50%* is randomly selected. For siblings to share DNA, they must inherit the *same segments* from both parents. 2. **Probability Calculation**: - For **each parent**, the chance both siblings inherit the same DNA is: \(0.5 \times 0.5 = 0.25\) (25% from mom + 25% from dad). - **Total**: \(25\% + 25\% = 50\%\) average shared DNA. 3. **Range of Variation**: Due to randomness, actual shared DNA varies between ~37.5% and ~62.5% (full siblings can share more or less than 50%, but 50% is the mean). 4. **Why the User’s Approach Flawed**: Adding 50% from each parent (50% + 50% = 100%) misrepresents inheritance as *non-overlapping* contributions. Instead, overlap determines shared DNA. **Final Answer**: Siblings share **~50% of their DNA** on average, calculated by the probability of overlapping inheritance from both parents (25% per parent), not by adding parental contributions. Actual shared DNA can vary within a range.