This document is a seminar submission on the topic of homopolymer tailing. It introduces homopolymer tailing as a method for joining DNA molecules by annealing complementary homopolymer sequences. Specifically, it involves adding homopolymer sequences like oligo(dA) to the 3' ends of one DNA molecule and complementary sequences like oligo(dT) to another molecule. This is done using the enzyme terminal deoxynucleotidyl transferase. The molecules can then be incubated to allow the complementary homopolymer sequences to anneal together via hydrogen bonding. Common applications include using poly dC tails on vectors and poly dG tails on DNA fragments to be cloned, in order to ligate the two molecules together

1. SEMESTER – IV
BIOTECHNOLOGY
SEMINAR TOPIC : HOMOPOLYMER TAILING
SUBMITTED BY,
S. JENIFER JULIE
II M.SC MICROBIOLOGY
REG NO : 20201232516107
SUBBMITED TO,
Dr. G. RAMANADHAN
DEPARTMENT OF MICROBIOLOGY

2. INTRODUCTION
• A homopolymer is a polymer where all the
subunits are same.
• Tailing is the adding a series of nucleotides on to
the 3’ –OH termini of a double stranded DNA
molecule using enzyme terminal
deoxynucleotidyl transferase of calf thymus.
• In homopolymer tailing , gene of interest is tailed
with one nucleotide and vector is tailed with an
complemetary base.

3. • It is the method for joining DNA molecules by
annealing of complementary homopolymer
sequence.
• Oligo(dA) sequences is added to the 3’ ends of
the molecule and oligo(dA) blocks to the 3’end
of another molecule.
• This method is catalyzed by enzyme terminal
deoxynucleotidyl transferase by addition of
nucleotides to the 3’ end of a DNA fragment.

6. PROCESS
• They are then allowed to incubate together to
allow hydrogen bonding to bring them together .
• Homopolymer tailing is achieved by annealing.
• It is a technique by which sticky ends can be
produced on an blunt-ended DNA molcule.
• The reaction when carrid out in the presence of
on deoxynucleotide a homopolmer tail is
produced.

8. • For ligation of two tailed molecules the
homopolymers must be complementary.
• Poly dC tails are attached to the vector and poly
dG to the DNA to be cloned.

9. USES OF HOMOPOLYMER
TAILING
• This is more widely used approach for making
recombinant DNA.
• Segments of 50-100 poly A and poly G are
added to one fragment.
• Equal length segments of poly-T and poly-C are
added to the other fragment.

10. Homopolymer tailing to provide a priming site for second strand
synthesis. Dark blue shaded material is DNA. The light blue shaded
material is RNA.

11. Thank You.....