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Q.Amplification of DNA is always between two primers. Why?

Ans:

For the amplification of specific sequence of a DNA ,we use two primers,Forward and reverse

 primers.Both primers are designed so that primer anneal with one strand will have its 3’ endtowards the centre of sequence which we want to amplif.B this newl made strand will !e

made in that direction.Both primers are annealed at different strands i.e. one primer on sense

strand and other on antisense strand.

After the annealing of primers "as shown in figure a!ove# $aq polmerase snthesi%es

complementar DNA strands ! incorporating deo& ri!onucleotides at the 3’ end of each

 primer.After first ccle of '(), complementar strands of !oth DNA strand s are formed as

shown in figure !elow:

 

After first ccle, newl formed strands *A,*B will !e formed.Now second ccle will occur and

after second scle we will have four new DNA strands and total + strands as shown !elow:

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At this stage,All strands have our specific DNA sequence !ut none of them has e&act ends of

specific region.But after the third ccle this is accomplished and we have two DNA molecules of 

e&act sequence we want,as shown in fig !elow:

After each ccle,num!er of molecules of specific sequence increases and this will !e dominant

tpe.

Now, we can conclude that Specific sequence is amplified by using forward and reerse

primers on different strands in the way that their !" end should be towards our desired

sequence.