Multiple Choice
In a standard DNA extraction protocol, what is the primary purpose of adding isopropyl alcohol to the lysate?
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
DNA fragments can be separated by gel electrophoresis because they differ in which property that affects their migration through the gel under an electric field?
A
Length (size), which causes smaller fragments to migrate faster through the gel matrix
B
Net positive charge differences among DNA fragments at neutral pH
C
Degree of double-helix supercoiling, which is the main determinant of migration for all linear fragments
D
Nucleotide sequence, because gels separate fragments based primarily on base composition
Verified step by step guidance1
Understand that gel electrophoresis separates DNA fragments based on their physical properties that affect movement through a gel matrix under an electric field.
Recall that DNA molecules have a uniform negative charge due to their phosphate backbone, so charge differences among fragments are minimal and do not significantly affect migration.
Recognize that the degree of supercoiling mainly affects circular DNA, but linear DNA fragments are separated primarily by size, not supercoiling.
Know that nucleotide sequence or base composition does not significantly influence migration speed in standard agarose or polyacrylamide gels.
Conclude that the key property affecting migration speed is the length (size) of the DNA fragments, with smaller fragments moving faster through the gel pores.
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