Molecular Biology of the Gene

Question 1

plasmid transformation

Answer 1

Plasmid transformation is a process by which bacteria takes up DNA from its environment. Transformation is a common technique in molecular biology, because it is possible to choose or design plasmids to fit some experiment. The plasmid and the proteins produced by it are useful to molecular biologists.

Question 2

restriction digestion

Answer 2

Restriction digestion is a process that breaks DNA fragments into smaller pieces. Restriction enzymes help cut DNA into smaller pieces so that biologists can analyze the sequences more easily. Biologists also use restriction digests to open up a plasmid and recombine it with other parts of other plasmids.

Question 3

electrophoresis

Answer 3

Electrophoresis is a method that allows us to sort fragments of DNA by size. Smaller fragments of DNA can move more quickly through the gel than large fragments can, when the same electric field is applied. DNA is not visible to the naked eye, so ethidium, radiation or fluorescence can be used to read the gels.

Question 4

ligation

Answer 4

Ligation is the binding of two nucleotides at the “backbone” with a phosphodiester bond. An enzyme called DNA ligase is commonly used for ligation. Ligation occurs during DNA synthesis of the lagging strand and is used for recombinant plasmids.

Question 5

selection for recombinant plasmids

Answer 5

Selection for recombinant plasmids is a method for “purifying” a bacterial population that has taken up the desired plasmid. The researcher can vary the environment in which the bacteria are grown, with the plasmid designed to withstand the environmental stress. The plasmid must contain a “resistance gene” that has also been added to the recombinant plasmid along with the other desired genes.