Since you have a huge grant for this project and you prefer
to save time, you have purchased the "Home made" cDNA library derived by
RT-PCR from malignant breast tissue expressing Cancer Antigen1.
You received a mixture of plasmids, each supposed to
contain one cDNA fragment corresponding to one mRNA species derived from
the malignant breast tissue. All these plasmids contain the lacZ
gene. Within this gene lies the multiple cloning site [MCS]
(this is shown in panel A). When the lacZ
gene is expressed by the bacteria, the bacteria colonies are colored blue.
If a DNA fragment is
inserted
to the MCS (as is done during library
construction) the lacZ gene is
disrupted (shown in panel B). Bacteria incorporating these plasmids will
give rise to white colonies.
A.
Blue Colonies
|
B.
White Colonies
|
You transformed bacteria with this plasmid mixture and
plated the bacteria-plasmids mixture on agar plates. Below you can see
4 different plates derived by 4 different students following bacteria transformation
with the plasmid mixture.
2. What are the small circles you
observe in the different plates?
a.
bacteria colonies containing no plasmids.
b.
bacteria colonies containing plasmids.
c.
plasmids.
