Which of the following modifications is most likely to alter the rate at which a dna fragment moves through a gel during electrophoresis? radioactively labeling the cytosine bases within the dna fragment increasing the length of the dna fragment leaving the length of the dna fragment the same altering the nucleotide sequence of the dna fragment without adding or removing nucleotides

increasing the length of the DNA fragment

Explanation:

DNA gel electrophoresis is a method often used in molecular biology, for the separation and analysis of DNA fragments.

Just like the name says it is performed on the gel (e.g. agarose gel) and electric field is applied for the separation of negatively charged DNA fragments. Fragments are separated by size, length (short fragments travel faster towards the positive electrode). Results of the gel electrophoresis are visualized via a DNA-binding dye and UV light and compared with standard reference called DNA ladder.

So, changing the length of DNA fragment, affects its movement through the gel.

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.