Cloning Vectors

Correct answer: A. DNA carrier with ori marker and cloning site

At easy level treat cloning vector as a DNA carrier with ori marker and cloning site. Questions are built from these functions.

Correct answer: A. Ori replication marker selection cloning site insertion

Ori is for replication marker is for selection and cloning site is for insertion. This is the most useful comparison.

Correct answer: A. Selecting transformed cells will be difficult

Ori helps in replication but marker is needed for selection. Without marker identifying transformed cells is difficult.

Correct answer: A. The vector will not replicate autonomously in the host cell

The ori (origin of replication) is the DNA sequence from which vector replication begins. Without an ori, the vector cannot replicate autonomously in the host cell and will not be stably maintained as cells divide. A selectable marker may help in selection, but it cannot compensate for the absence of ori. Exam tip: remember that ori is required for replication, whereas a selectable marker is used to identify or select transformed cells.

Correct answer: A. Controlled insertion at designed restriction site

MCS provides many designed restriction sites. This allows the insert to be added at a controlled position.

Correct answer: A. It may have a vector with resistance marker

Growth on antibiotic can indicate a transformed cell. But screening may be needed to confirm recombinant status.

Correct answer: A. Selection chooses transformed cells and screening identifies recombinants

Antibiotic selection chooses vector-containing cells. Blue-white screening helps identify insert-containing recombinants.

Correct answer: A. Blue colony

A blue colony can indicate active lacZ. It generally shows a non-recombinant vector without insert.

Correct answer: A. White colony

A white colony can indicate a recombinant clone due to lacZ disruption. Remember it as a screening result.

Correct answer: A. Selecting ampicillin-resistant transformed cells

ampR gene gives ampicillin resistance. Thus vector-containing cells can grow on an ampicillin plate.

Correct answer: A. Insertional inactivation

An insert can disrupt a marker gene. This can identify recombinants by insertional inactivation.

Correct answer: A. Transformation may become less easy

Very large vectors can be difficult to introduce into a host. Therefore small size is a common vector feature.

Correct answer: A. When more plasmid DNA is needed

A high-copy-number plasmid is maintained in many copies per host cell, provided that the vector and host system support such maintenance. This feature is useful when the experiment requires a larger yield of plasmid DNA, for example for restriction analysis, sequencing, further cloning, or preparation of a DNA sample. Therefore option A is correct. High copy number does not mean that DNA is removed, that cells are destroyed, or that proteins are digested. The governing trade-off is that increasing copy number can improve DNA yield but may also place a metabolic burden on the host or reduce stability for some inserts. Thus copy number is selected according to the purpose of the cloning experiment.

Correct answer: A. YAC

The direct answer is A, YAC. A very large DNA fragment needs a carrier that can hold much more DNA than an ordinary small plasmid. YAC means yeast artificial chromosome. It contains chromosome-like features that allow large foreign DNA fragments to be maintained in yeast, so it is suitable for very large genomic inserts. Option A works because YACs were designed for large DNA cloning. Option B, a small pUC plasmid, is useful for ordinary smaller inserts but has a much lower carrying capacity, so it is not the best choice here. Option C, pepsin, is a protein-digesting enzyme, not a DNA vector. Option D, amylase, digests starch and is also not a vector. Exam cue: artificial chromosomes are chosen when the insert is too large for a normal plasmid.

Correct answer: A. BAC

BAC stands for bacterial artificial chromosome. It is a bacteria-based cloning vector used to clone relatively large DNA fragments. YAC stands for yeast artificial chromosome, so it is the closest but incorrect option. MCS is a short region containing cloning sites, whereas lacZ is a reporter gene. Exam tip: Link BAC with bacteria and YAC with yeast to remember the abbreviations.

Correct answer: A. YAC

YAC stands for yeast artificial chromosome. It is a cloning vector designed to function like a chromosome in yeast cells and can carry very large DNA fragments. BAC is also used for cloning large DNA fragments, but it stands for bacterial artificial chromosome. Exam tip: Associate YAC with yeast and BAC with bacteria.

Correct answer: A. Agrobacterium tumefaciens

Ti plasmid is found in Agrobacterium tumefaciens. Modified Ti plasmid is useful in plant transformation.

Correct answer: A. T-DNA

The T-DNA of Ti plasmid is transferred into plant cells. In biotechnology it is used after modification.

Correct answer: A. Bacteriophage vector

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

Correct answer: A. Lambda phage DNA packaging

A cosmid carries cos (cohesive-end) sites derived from bacteriophage lambda. These sites are required for packaging DNA into lambda phage particles, so lambda phage DNA packaging is correct. The origin of replication is a separate plasmid sequence and is not the function of a cos site. Exam tip: remember that cosmids combine useful features of plasmids and lambda phage.

Correct answer: A. Small circular double-stranded DNA

The direct answer is A: a plasmid vector is usually a small, circular, double-stranded DNA molecule. To understand this, a plasmid is an extra DNA molecule found independently of the main bacterial chromosome. It can often replicate because it has an origin of replication, and a vector may also contain a selectable marker and cloning site. Option A is correct because it describes the basic physical form of most plasmid vectors. Option B is wrong because a protein chain is not DNA and cannot itself be called a plasmid. Option C is wrong because a fat droplet is a lipid structure, not genetic material. Option D is wrong because chlorophyll is a pigment involved in photosynthesis, not the structure of a vector. Some special plasmids may differ in details, but the basic school-level description remains circular double-stranded DNA. Memory cue: plasmid equals small extra ring of DNA.

Correct answer: A. DNA ligase

Restriction enzymes can prepare ends but DNA ligase performs joining. It makes the recombinant vector.

Correct answer: A. Insert orientation control

Directional cloning uses different ends to help insert DNA in the desired direction. It can be useful in expression experiments.

Correct answer: A. Cloning vector with ori marker and cloning site

A simple cloning vector may be enough for DNA copy production. Expression may need extra elements like a promoter.

Correct answer: A. To see expected DNA fragment pattern

Restriction digestion can indicate presence and size of insert in a vector. Gel pattern helps in confirmation.