DNA Extraction and Analysis Flashcards
6 cards from real BACE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 DNA Extraction and Analysis flashcards as text
What is the role of SDS (sodium dodecyl sulfate) in a DNA extraction lysis buffer?
Answer: It denatures and solubilizes proteins, disrupts cell membranes, and helps release nucleic acids
SDS is an anionic detergent that disrupts lipid bilayers, denatures proteins (including nucleases), and releases cellular contents including DNA.
In gel electrophoresis of DNA, what determines the direction and rate of DNA migration?
Answer: DNA migrates toward the positive electrode (anode) because it is negatively charged; smaller fragments migrate faster
DNA has a uniform negative charge from its phosphate backbone and migrates toward the positive anode; smaller fragments move faster through the gel matrix than larger ones.
What is the purpose of adding ethanol during a silica membrane DNA purification protocol (spin column)?
Answer: To bind DNA to the silica membrane by reducing aqueous solvation of DNA
Ethanol (typically with a chaotropic salt wash buffer) reduces the hydration shell around DNA molecules, promoting their adsorption to the negatively charged silica membrane.
A DNA sample shows an A260/A280 ratio of 1.5 when measured by spectrophotometry. What does this indicate?
Answer: The DNA sample is likely contaminated with protein, which absorbs strongly at 280 nm
Pure double-stranded DNA has an A260/A280 ratio of ~1.8; a ratio of 1.5 indicates protein contamination since proteins absorb at 280 nm, reducing this ratio.
What is restriction fragment length polymorphism (RFLP) analysis used for?
Answer: Identifying DNA sequence differences between individuals by digesting DNA with restriction enzymes and comparing fragment sizes
RFLP analysis detects DNA sequence variations by using restriction enzymes to cut DNA at specific recognition sites; sequence differences create different fragment size patterns on gels.
Why is EDTA (ethylenediaminetetraacetic acid) often included in DNA storage and elution buffers (TE buffer)?
Answer: It chelates divalent metal ions (Mg2+, Mn2+) required by DNase enzymes, preventing DNA degradation
EDTA chelates Mg2+ and other divalent cations required as cofactors by DNase enzymes, inhibiting their activity and protecting stored DNA from degradation.