A researcher isolates a specific double-stranded DNA fragment that...

The distance between two consecutive base pairs in a typical B-DNA double helix is $0.34 \text{ nm}$ or $0.34 \times 10^{-9} \text{ m}$.

The total length of the DNA fragment is calculated by multiplying the total number of base pairs by the distance between two consecutive base pairs.

$\text{Length} = 2 \times 10^{5} \times 0.34 \times 10^{-9} \text{ m}$

$\text{Length} = 0.68 \times 10^{-4} \text{ m}$

Converting meters to micrometers ($\mu\text{m}$), where $1 \text{ }\mu\text{m} = 10^{-6} \text{ m}$:

$\text{Length} = 68 \times 10^{-6} \text{ m} = 68 \text{ }\mu\text{m}$

Answer: $68 \text{ }\mu\text{m}$