(i) Describe the characteristics a cloning vector must possess.
(ii) Why DNA cannot pass through the cell membrane? Explain. How is a bacterial cell made ‘competent’ to take up recombinant DNA from the medium?
Answers
Answer:
1.հίίί ʍαtε_______✯◡✯
.
.
.
.
_________________________
һєяє' ʏȏȗя ѧṅśwєя ʟȏȏҡıṅɢ ғȏя________
.
✯The characteristics a cloning vector must possess are:--
____________
1)ORIGIN OF REPLICATION(ORI):--
===============================
__ ★this is a sequence from which replication starts and any piece of DNA when linked within the host cells.This sequence is also responsible for controlling the copy number of the linked DNA.
________________
2)SELECTABLE MARKERS:--
==========================
___★It is a gene which helps in indentifying and eliminating non-transformantsb and selectively permitting the growth of the transforments .The genes encoding resistance to antibiotics such as amplicillin ,chlroamphenicol, tetracycline or kanamycin it
etc.are considered as useful selectable markers for E.coli.The normal E.coli cells do not carry resistance against any of these antibiotocs.
________________
3) CLONING SITES:-
===================
___ ★In order to link the alien DNA ,the vector needs to have very few .preferably single recognition site for the commonly used restriction enzymes.
Another desirable feature of a cloning vector is that it should be relatively small in size since large molecules tend to break down during purification and are also difficult to manipulate.
_________
2.As DNA is a highly hydrophilic molecule, normally it cannot pass through the cell membrane of bacteria. Hence, in order to make bacteria capable of internalizing the genetic material, they must be made competent to take up the DNA.