Question

a scientist used laboratory techniques to move gene x from a bacteria-specific plasmid into a yeast-specific plasmid. to do this, the scientist first used restriction enzymes to digest, or cut, the bacteria-specific plasmid on either side of the gene, which resulted in a mixture of two linear pieces of dna (figure 1).
figure 1. diagram showing the bacterial plasmid before and after restriction enzyme digestion (bp = base pairs).
the scientist used gel electrophoresis to separate the resulting dna fragments by size. then, the scientist cut out the area of the gel containing gene x in order to purify the gene from the gel.
the following diagram shows the digested plasmid dna as visualized by gel electrophoresis, with various bands labeled a, b, and c. which of the bands did the scientist cut out in order to isolate gene x dna?
choose 1 answer:
a band a
b band b
c band a and band b
d band c

Explanation:

1. From Figure 1, Gene X is on a DNA fragment of 1,890 bp after restriction enzyme digestion.
2. In gel electrophoresis, smaller DNA fragments move faster (travel farther) than larger ones. The DNA ladder shows band positions: Band B is near the 2,000 bp marker, and 1,890 bp is close to 2,000 bp. Band A is near 3,000 bp (too large), Band C is smaller than 2,000 bp (too small). So Band B corresponds to the 1,890 bp Gene X fragment.

Answer:

B. Band B