Multiple Choice
Which career most directly combines DNA technology (e.g., DNA profiling) with forensic investigations to help identify individuals from biological evidence?
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
In gel electrophoresis, what is the purpose of a DNA ladder?
A
To provide a set of DNA fragments of known sizes that serves as a molecular size standard for estimating the lengths of sample DNA fragments
B
To stain DNA so that bands become visible under UV light
C
To cut DNA at specific restriction enzyme recognition sites to generate fragments
D
To amplify a specific DNA region through repeated thermal cycling
Verified step by step guidance1
Understand that gel electrophoresis is a technique used to separate DNA fragments based on their size by applying an electric field to a gel matrix.
Recognize that after running the gel, DNA fragments appear as bands, but to determine the size of these fragments, a reference is needed.
Know that a DNA ladder is a mixture of DNA fragments of known lengths that is run alongside the sample DNA in the gel.
Use the DNA ladder bands as a molecular size standard by comparing the position of sample DNA bands to the ladder bands to estimate their sizes.
Conclude that the primary purpose of the DNA ladder is to provide a size reference, not to stain DNA, cut DNA, or amplify DNA regions.
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