Cloning Vectors

Correct answer: A. Blue-white selection

Insertion into lacZ changes colony color in blue-white screening. This helps identify recombinants.

Correct answer: A. As independent circular DNA

Plasmids are independent DNA molecules separate from the chromosome. They can replicate due to their origin.

Correct answer: A. Ori and selectable marker

Ori allows replication and marker helps in selection. Both are important for vector maintenance.

Correct answer: A. Recombinant vector

When insert DNA is added the vector becomes a recombinant vector. This is the main product of a cloning experiment.

Correct answer: A. DNA ligase

During recombinant-DNA construction, the vector and insert are first prepared so that their ends can align, often by using the same restriction enzyme or compatible ends. DNA ligase then catalyses phosphodiester-bond formation between the aligned ends, creating a stable recombinant vector that carries the insert. Thus option A is correct. Pepsin is a protein-digesting enzyme active mainly in the stomach, and lipase breaks down fats; neither acts on DNA ligation. Chlorophyllase is associated with pigment metabolism in plants and has no role in joining a DNA insert to a cloning vector. The key sequence is cut, align, and ligate.

Correct answer: A. To select transformed cells on antibiotic medium

Cells with a resistance marker can grow on the related antibiotic. This allows selection of transformed cells.

Correct answer: A. Selectable marker

Ampicillin resistance gene is a useful marker for selection. It helps identify transformed cells.

Correct answer: A. It is cut with a restriction enzyme

The vector is cut at a suitable restriction site to create space for the insert. Then ligase joins it.

Correct answer: A. Escherichia coli

Escherichia coli is a very common host for plasmid cloning. It grows fast and is easy to handle in the lab.

Correct answer: A. To make many copies of it

The vector carries foreign DNA into a host where copies can be made. This is the main purpose of cloning.

Correct answer: A. It acts as a DNA carrier

A cloning vector is a DNA molecule, such as a plasmid, that carries a desired DNA fragment into a host cell and helps it produce copies there. Therefore, it acts as a DNA carrier. Digestive enzymes act on food molecules such as fats; they do not deliver DNA into a host. Exam tip: Remember the key vector features—an origin of replication, a selectable marker, and a cloning site.

Correct answer: A. It helps open the vector at one defined place

A unique restriction site is useful for controlled insertion. It avoids unwanted cutting at many places in the vector.

Correct answer: A. It will be difficult for the vector to make copies in host

Origin of replication is needed for vector replication. Without it DNA copies will not increase in cloning.

Correct answer: D. Chlorophyll pigment

A cloning vector needs ori selectable marker and cloning site. Chlorophyll pigment is not an essential part of a cloning vector.

Correct answer: A. For selection or screening

A marker gene helps identify transformed or recombinant cells. It makes a cloning experiment practical.

Correct answer: A. When the insert gene needs to be expressed

In expression vectors promoter is needed for gene expression. In simple cloning vectors the main focus is making DNA copies.

Correct answer: A. Expression vector helps produce gene product

A cloning vector is for making DNA copies. An expression vector helps gene expression and product formation.

Correct answer: A. BAC

BAC is useful for cloning large DNA fragments. At easy level remember it as a large insert vector.

Correct answer: A. Cloning very large DNA inserts

YAC can be useful for carrying very large DNA inserts. Link it with yeast-based large insert vectors.

Correct answer: A. Virus that infects bacteria

A bacteriophage is a virus that infects bacteria. Modified phage vectors can be useful in DNA cloning.

Correct answer: A. To make copies of vector and insert

A host cell can replicate the recombinant vector. This produces many copies of the desired DNA.

Correct answer: A. Ori selectable marker and cloning site

A good cloning vector should have parts like ori marker and cloning site. They help in replication selection and insertion.

Correct answer: A. DNA ligase

DNA ligase joins the foreign gene and vector ends. Restriction enzymes can create compatible ends first.

Correct answer: A. Carrying desired DNA into host and making copies

A vector carries desired DNA into a host and helps replication. Therefore a vector is necessary in gene cloning.

Correct answer: A. Selectable marker

A selectable marker shows which cells are growing with the vector. It helps identify transformed cells.