Starting base pair by G:C (A:T®I:T®G:C) (Gaudelli et al.

Starting in 2016, the above hybrid ‘Target-AID’ system of cytosine
deaminases was extensively used for developing a large number of plasmid
vectors (Komor et al., 2016), which were described as base editors (BEs). These
BEs were successfully used  for generating
precise C®T mutations in a
number of mouse/Xenopus/human living
cells and embryos. In case of mouse and Xenopus,
the modified embryos were also used for transplantation in surrogate mothers
for generating offsprings exhibiting altered phenotypes (e.g., black to albino
body colour). In plant systems also, protoplasts were successfully used for
creating mutations in specific genes, and then regenerated into whole plants
exhibiting desirable altered traits. In 2017, adenine deaminases were also
developed in the laboratory, so that adenine base editors (ABE) became
available for conversion of adenine into inosine, so that it became possible to
replace A:T base pair by G:C (A:T®I:T®G:C) (Gaudelli et al. 2017). In this manner
CRISPR/Cas was modified and used in the form of BEs, and ABEs, which brought
mani fold efficiency and precision to gene editing technology.

      The technique of single base editing was particularly developed
and nurtured by a team of workers, which was led
by David Lui (Fig. 2), a Professor of Chemistry and Chemical Biology at Harvard
University. He is also a core member of the internationally known Broad
Institute of MIT in USA. Keeping in view the revolution that BEs brought in gene
editing technology during 2016-17, David Lui was listed as first of the ten people, who mattered in the year
2017 according to Nature10 (Volume 552, Issue 7685). In the present article, an
attempt has been made to describe this new approach of single base-editing and
to review the progress made in this subject during 2016 and 2017. The author
hopes that the
article will prove useful
for teachers and students in developing
awareness about this very active
and exciting area of research. The progress made in the development and use of BEs
was summarized in five articles that
appeared in a special issue of Nature Biotechnology in May 2017
(see later). These five papers included papers
on base editing in mouse embryos as well as in crops including rice, wheat, maize and tomato.

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