The length of the minimum unique stretch of DNA sequence that can be found only once in a 3 billion base pairs long genome is ?

Question

Sebastian Alvarado · Accepted Answer

Theoretically that would be 1.5 billion +1 base pairs...

Actually, you can't tell because most DNA molecules contain sizable portions of "spacer" DNA.

Penelope Adams · Answer

undefined It depends on the specifics of the genome and the characteristics of the DNA sequences present, making it challenging to determine a precise length without additional information.

HIX Tutor · Answer

undefined To find the length of a unique stretch of DNA in a very large genome, we can use a general rule of thumb.

1. **Understand the Genome Size**: The genome is about 3 billion base pairs long.

2. **Unique DNA Sequence**: A unique stretch means it only appears once in the entire genome.

3. **DNA Bases**: DNA has 4 types of bases: A, T, C, and G.

4. **Calculate Stretches**:
   - For a stretch of length $L$, the number of possible unique sequences is $4^L$.
   - To find the smallest $L$ such that $4^L$ is at least 3 billion (3,000,000,000).

5. **Trial and Error**:
   - For $L = 5$: $4^5 = 1024$ (too small)
   - For $L = 10$: $4^{10} = 1,048,576$ (still too small)
   - For $L = 15$: $4^{15} = 1,073,741,824$ (this is enough)

6. **Conclusion**: The minimum unique stretch length of DNA that can be found only once in a 3 billion base pair genome is **15 base pairs** long.