Competent Host

Correct answer: A. Empty vector self-ligation

An empty vector can be selected due to the marker but lacks insert. It is identified by screening.

Correct answer: A. Sensitive cells grow around antibiotic breakdown

Some antibiotics can become less effective near resistant colonies. This can produce small satellite colonies.

Correct answer: A. Identifying contamination or mixed colonies

Colony appearance can indicate contamination. Molecular tests are needed for insert confirmation.

Correct answer: A. DNA sequencing

Sequencing can confirm insert identity orientation and mutations. Therefore it is strong for final verification.

Correct answer: A. For long-term preservation

A glycerol stock preserves the clone for future use. This allows the same clone to be used again.

Correct answer: A. To protect cells from freezing damage

Glycerol is added to a glycerol stock because it acts as a cryoprotectant during frozen storage. It helps reduce the formation and harmful effects of ice crystals, limits severe changes in the cell’s surroundings, and improves the chance that cells will remain viable after thawing. Therefore, option A is correct. Glycerol does not cut DNA; that function belongs to restriction enzymes. It does not itself transform a host cell, which requires introducing genetic material by an appropriate method, and it is not added simply to colour proteins. The governing idea is preservation of living cells at low temperature.

Correct answer: A. Strain name, plasmid, marker, and date

A clone stock label should contain enough information to identify the biological material and reconstruct its history. Option A is correct because the strain name identifies the host, the plasmid or construct identifies the recombinant DNA, the selectable marker helps distinguish the maintenance condition, and the date supports age and storage tracking. Depending on laboratory practice, an operator name, clone number, storage temperature, or passage information may also be added. Water taste and plate smell are not reproducible identifiers, while protein color alone cannot establish which strain or construct is present. Clear labeling prevents mix-ups and supports reproducibility.

Correct answer: A. Efficiency screening confirmation and troubleshooting are connected

In competent host workflow uptake selection screening and confirmation are connected. Controls make results reliable.

Correct answer: A. DNA enters host selected colonies are screened and confirmed

A competent host takes up DNA. Then the correct clone is chosen by selection screening and confirmation.

Correct answer: A. A cell that can take up external DNA

In recombinant DNA work, a competent host is a cell that has been made capable, naturally or artificially, of taking up foreign or external DNA from its surroundings. Option A is correct. After uptake, the DNA may be maintained as a plasmid or incorporated into the host genome, and the resulting event is commonly called transformation. Chemical treatment or electroporation can increase competence in laboratory cells. A competent host is not an enzyme, pigment, or mineral: those substances have different biological roles and cannot serve as living recipient cells for recombinant DNA.

Correct answer: A. Ability to take up external DNA

In genetic engineering, competence is the ability of a bacterial cell to take up external or foreign DNA. The entry of DNA into such a competent cell is associated with transformation. Protein digestion is not related to cellular competence. Exam tip: remember competence as DNA uptake for transformation.

Correct answer: A. Entry of external DNA into host cell

In transformation external DNA is introduced into a host cell. Competent cells are useful in this process.

Correct answer: A. It can take up plasmid DNA

A competent cell can take up plasmid or recombinant DNA. This is the basis of cloning transformation.

Correct answer: A. By selectable marker based growth

A selectable marker lets transformed cells grow on selection medium. It gives initial identification.

Correct answer: A. Screening or molecular confirmation

Selection may only show vector uptake. PCR digest or sequencing are useful for insert confirmation.

Correct answer: A. Calcium chloride and heat shock

Chemical transformation commonly uses calcium chloride and heat shock. This is a simple pair for bacterial competence.

Correct answer: A. Electroporation

Electroporation uses an electric pulse to increase DNA uptake. It can be considered a physical delivery method.

Correct answer: A. DNA-coated particles

A gene gun can deliver DNA-coated particles into plant cells. It is a direct DNA delivery method.

Correct answer: A. It can transfer DNA into plant cells

Agrobacterium is useful in plant transformation due to T-DNA transfer ability. It is called a natural genetic engineer.

Correct answer: A. Plant transformation may need regeneration step

Transformed plant cells may need to regenerate a whole plant. Bacterial colonies grow directly on plates.

Correct answer: A. To check whether cells and method are working

A positive control with known plasmid verifies competence and protocol. It helps in troubleshooting.

Correct answer: A. Checking contamination or background growth

A negative control is a reaction or transformation setup in which the test plasmid or other intended experimental factor is deliberately omitted. Its governing concept is baseline comparison: any colony or signal in this control should not be attributed to successful uptake of the target plasmid. If growth appears on a selective plate, it may indicate contamination, incorrect antibiotic concentration, degraded selection medium, or naturally resistant cells. Therefore, option A is correct because the control checks background growth and the cleanliness and validity of the selection system. Option B describes an experimental aim, while options C and D concern DNA synthesis or marker expression and are not purposes of a negative control.

Correct answer: A. Many factors like competence DNA and antibiotic can affect it

No growth can occur due to poor competence wrong antibiotic or DNA issue. Controls help identify the cause.

Correct answer: A. Weak selection or contamination

Background growth can come from weak antibiotic contamination or empty vector. Screening and controls are needed.

Correct answer: A. Vector can replicate and express in host

In host-vector compatibility elements like ori marker promoter work in the host. This is needed for success.