Blue White Colonies

richardtoh2000 at richardtoh2000 at
Tue Feb 24 12:13:32 EST 2004

I am doing a project to clone the DNA fragment encoding mouse beta-actin into the
pGEM-T vector by using TA cloning. My results as below:

Reaction	                       Blue Colonies	                      White Colonies	
	              Number	Percentage (%)	Number	Percentage (%)Standard Reaction	130	90.3	                14	9.7	
(with PCR product)

Positive Control	76	71.0	                31	29.0	
(Control Insert)

Background Control	36	100.0	                0	0	

My questions as below:
1. why is the number of blue colonies in both the SR and PC higher than the white?
2. i suppose to observed only white colonies in both SR and PC but blue colonies also turn up. why is that so?
3. BC should not have any colony but the result shows it does. why is that so?

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