Final answer:
A 5,000 base-pair double-stranded DNA molecule is 1.7 micrometers long as each base pair is 0.34 nanometers apart and there are 5,000 of them.
Step-by-step explanation:
To calculate the length of a double-stranded DNA molecule that is 5,000 base-pairs long, we need to consider that each base pair is 0.34 nanometers (nm) apart, as deduced by Watson and Crick when they described the structure as a double helix. Since there are 10 base pairs per turn of the helix and each turn is 3.4 nm, we calculate the length of the DNA molecule by multiplying the number of base pairs by the distance between them:
Length = Number of base pairs × Distance between base pairs
Length = 5,000 base pairs × 0.34 nm/base pair
Length = 1,700 nm or 1.7 micrometers (μm), which is equivalent to option (c) 1.7 um.
Therefore, the molecule is not 170 nm, 500 Angstroms (A), 0.17 mm, or any other length stated in the options provided.