Blue-White Screening and PUC Vectors

The video tutorial explains the PUC vector, a modified version of the pBR322 vector, highlighting its features such as high copy number and selectable markers. It details the process of gene insertion and inactivation, and how blue-white screening is used to differentiate between recombinant and non-recombinant colonies. The advantages of the PUC vector, including easy selection and multiple restriction sites, are discussed, along with its limitation of small fragment size.

What is the primary advantage of PUC vectors over pBR322?

• Larger size

• More selectable markers

• Higher copy number

• Fewer restriction sites

Which gene in PUC vectors provides resistance to antibiotics?

• Ori gene

• LacZ gene

• Ampicillin resistance gene

• Beta-galactosidase gene

What is the role of the LacZ gene in PUC vectors?

• Acts as a cloning site

• Forms beta-galactosidase enzyme

• Provides antibiotic resistance

• Initiates replication

What happens to the LacZ gene during insertional inactivation?

• It becomes more active

• It is deleted

• It becomes non-functional

• It duplicates

How many types of colonies are formed after transformation in blue-white screening?

• Three

• Two

• Four

• One

What color do non-recombinant colonies appear in blue-white screening?

• Green

• Blue

• White

• Red

What is the function of IPTG in blue-white screening?

• Induces beta-galactosidase gene

• Inhibits colony growth

• Acts as a repressor

• Provides antibiotic resistance

What is a disadvantage of PUC vectors?

• Limited restriction sites

• Complex selection process

• Small fragment size

• Low copy number

What is the maximum fragment size that PUC vectors can accommodate?

• 10 kb

• 15 kb

• 20 kb

• 25 kb

What is the main advantage of PUC vectors in terms of colony selection?

• Faster replication

• Larger cloning capacity

• Color-based selection

• Multiple antibiotic resistances