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

It precipitates DNA out of solution for easy collection

Answer

It inhibits DNase enzymes that would degrade DNA

Answer

It chelates magnesium ions required for membrane stability

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 migrates toward the negative electrode because it is positively charged; larger fragments migrate faster

Answer

DNA migrates based on base composition (GC content) regardless of size

Answer

All DNA fragments of the same base pair length migrate at exactly the same speed regardless of gel percentage

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

To digest proteins and cellular debris that would clog the membrane

Answer

To elute purified DNA from the column for downstream use

Answer

To denature double-stranded DNA into single strands for PCR

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

The DNA is very pure with no protein contamination

Answer

The sample contains RNA but no protein contamination

Answer

The concentration of DNA is too low to measure accurately

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

Amplifying specific DNA sequences using thermal cycling

Answer

Sequencing the complete genome of an organism

Answer

Measuring the concentration of DNA in a solution

Question 6

Why is EDTA (ethylenediaminetetraacetic acid) often included in DNA storage and elution buffers (TE buffer)?

Accepted Answer

It chelates divalent metal ions (Mg2+, Mn2+) required by DNase enzymes, preventing DNA degradation

Answer

It increases DNA solubility in aqueous solutions

Answer

It acts as an antifungal agent to prevent microbial growth in DNA stocks

Answer

It provides a reducing environment to prevent DNA oxidation