Multiple Choice
In forensic DNA analysis, which part of a hair is most likely to contain nuclear DNA suitable for STR profiling?
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18. Molecular Genetic Tools
Methods for Analyzing DNA
Multiple Choice
In agarose gel electrophoresis, what is the primary purpose of a DNA ladder?
A
To ligate DNA fragments together by catalyzing phosphodiester bond formation
B
To denature double-stranded DNA into single strands prior to electrophoresis
C
To provide a set of DNA fragments of known sizes used to estimate the length (in base pairs) of sample DNA fragments
D
To stain DNA so bands can be visualized under UV or blue light
Verified step by step guidance1
Understand that agarose gel electrophoresis is a technique used to separate DNA fragments based on their size by applying an electric field to move negatively charged DNA through a gel matrix.
Recognize that a DNA ladder (also called a molecular weight marker) consists of DNA fragments of known lengths, which serve as reference points during electrophoresis.
During the run, the DNA ladder is loaded into one well of the gel alongside the sample DNA fragments.
After electrophoresis, the DNA ladder bands appear at specific positions corresponding to their known sizes, allowing comparison with sample bands.
Use the positions of the ladder bands to estimate the sizes of unknown DNA fragments by comparing their migration distances relative to the ladder.
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