Why are some colonies blue and some white?
Table of Contents
Why are some colonies blue and some white?
Any colony containing the plasmid (and therefore the functioning β-galactosidase gene) will turn blue, a result of the β-galactosidase activity. The insert disrupted the β-galactosidase gene, and therefore these colonies remain white.
What does a white colony indicate during blue white screening explain how the color is formed?
How Does Blue White Screening Work? For screening the clones containing recombinant DNA, a chromogenic substrate known as X-gal is added to the agar plate. The colonies formed by non-recombinant cells, therefore appear blue in color while the recombinant ones appear white.
What do blue colonies represent?
Answer c. Blue colonies represent cells containing empty plasmid vectors. The Ti plasmid is used for introducing genes into: animal cells.
What do blue colonies represent in blue white screening?
Blue colonies therefore show that they may contain a vector with an uninterrupted lacZα (therefore no insert), while white colonies, where X-gal is not hydrolyzed, indicate the presence of an insert in lacZα which disrupts the formation of an active β-galactosidase.
What is blue-white screening Slideshare?
I) BLUE-WHITE SCREENING The use of chromogenic substrate to detect a particular enzymatic activity is the basis to screen the desired clone. The colourless compound X-gal or 5-bromo-4-chloro-3-indolyl-β-D-galactoside used in this screening method is a substrate for β-galactosidase.
Can you do blue-white screening without IPTG?
In some blue/white screening systems, an additional reagent must be used: IPTG (isopropylthiogalactoside). IPTG is an inducer that de-represses lacZ expression (it turns the gene on). In some cases, without IPTG, not enough β-galactosidase is produced to turn the colony blue even if the lacZ gene is intact.
What is blue white screening and what is alpha complementation?
Blue-white screening in the lab Providing DNA encoding this section of amino acids (called the α-peptide) to a lacZΔM15-mutant bacterial cell in trans complements the mutation allowing for a functional enzyme. This process is called α-complementation.
When performing a blue-white screen white bacterial colonies contain?
These white colonies contain the recombinant bacteria and should be selected (Figure 1). Here, we describe a protocol to perform effective blue-white colony screening to select the recombinant bacteria carrying your DNA of interest.
What is selection of recombinants?
Selection is where some sort of pressure (e.g. the presence of an antibiotic) is applied during the growth of host cells containing recombinant DNA. The cells with the desired characteristics are therefore selected by their ability to survive.
What is insertional activation?
Definition. Insertional activation/inactivation refers to either activation of an endogenous gene which is located near an integrated transgene, or to disruption of a gene or other functional sequence by insertion of a transposable element.
What are the process of selection of recombinant cells?
– The host cells containing recombinant will form white coloured substrate on the medium containing X-gal. – The host cells containing non recombinants wil turn blue in colour. – On the basis of colony colour the recombinants can be selected.