A blot band is dark. What does that mean after checking the loading control?

• The protein weighs exactly that many grams
• The protein is present in a rough amount
• The antibody has failed completely

A gentle first spin drops one organelle. Which one?

• Nuclei
• Mitochondria
• Ribosomes

A pull-down hit proves the two proteins touch each other directly.

What are the three stages of a Western blot?

• Fix cells, add GFP tag, film over time
• Spin nuclei, spin mitochondria, spin ribosomes
• Separate on gel, transfer to membrane, probe with antibody

Why does SDS let a gel sort by size alone?

• SDS dyes every protein a different colour
• SDS cuts all proteins to equal length
• Detergent equalizes charge so only size decides speed

What does the loading control correct for?

• Wrong antibody colour
• Uneven filling of the lanes
• Too much microscope zoom

A brief binding partner never shows in a pull-down. Why?

• Beads only grab DNA
• Weak partners wash away before reading
• Gels cannot show small proteins

One lane is empty but its loading control band is healthy. What do you conclude?

• The gel ran backwards
• The control proves the protein is there
• The protein is absent or vanishingly low