BACE DNA Extraction and Analysis 2

Question 1

What is the role of SDS (sodium dodecyl sulfate) in a DNA extraction lysis buffer?

Accepted Answer

It denatures and solubilizes proteins, disrupts cell membranes, and helps release nucleic acids

Answer

SDS is an anionic detergent that disrupts lipid bilayers, denatures proteins (including nucleases), and releases cellular contents including DNA.

Question 2

In gel electrophoresis of DNA, what determines the direction and rate of DNA migration?

Accepted Answer

DNA migrates toward the positive electrode (anode) because it is negatively charged; smaller fragments migrate faster

Answer

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.

Question 3

What is the purpose of adding ethanol during a silica membrane DNA purification protocol (spin column)?

Accepted Answer

To bind DNA to the silica membrane by reducing aqueous solvation of DNA

Answer

Ethanol (typically with a chaotropic salt wash buffer) reduces the hydration shell around DNA molecules, promoting their adsorption to the negatively charged silica membrane.

Question 4

A DNA sample shows an A260/A280 ratio of 1.5 when measured by spectrophotometry. What does this indicate?

Accepted Answer

The DNA sample is likely contaminated with protein, which absorbs strongly at 280 nm

Answer

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.

Question 5

What is restriction fragment length polymorphism (RFLP) analysis used for?

Accepted Answer

Identifying DNA sequence differences between individuals by digesting DNA with restriction enzymes and comparing fragment sizes

Answer

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.

BACE - Biotechnician Assistant Credentialing Exam Practice Test

BACE - Biotechnician Assistant Credentialing Exam Practice Test

BACE DNA Extraction and Analysis 2