RNA Polymerase, Exons, Introns Video Lecture - NEET

RNA polymerases or enzymes that initiate
a new RNA chain on a DNA template there
are also such things as RNA directed RNA
polymerases for the purposes of
understanding synthetic biology you are
likely to encounter two of these enzymes
first is one that produces the RNAs in
the cell and the other is t7 RNA
polymerase though the native enzyme is
important to understand in the context
of gene expression only the phage one is
commonly used in vitro so we'll focus on
that one t7 RNA polymerase is used for
both in vivo and in vitro transcription
when people speak of t7 expression
systems the pet vectors BL 21 or D III
strains they are talking about systems
employing the t7 RNA polymerase to
control the transcription of an
engineered gene it produces very high
protein expression levels in vivo but it
also can be used to generate tRNAs mRNAs
or ribosomes and apt immers in vitro the
substrate for t7 RNA polymerase is a
double-stranded DNA with the t7 promoter
sequence shown here the polymerase binds
to the sequence displaces the sent
strand and initiates a new molecule from
a g residue at the end of the t7
promoter sequence when the polymerase
reaches either the end of the DNA which
is called run off transcription or when
it hits a terminator sequence the new
single-stranded RNA is released and
polymerization can begin again