In transcription, the mRNA strand is formed by complementary base pairing of the template DNA strand. However we should note that the nitrogenous bases in mRNA are Adenine, Guanine, Cytosine and
Uracil
, while those in DNA are Adenine, Guanine, Cytosine and
Thymine
.
So the mRNA strand would be formed by matching the
A in DNA with U in mRNA
,
T in DNA with A in mRNA
,
C in DNA with G in mRNA
and
G in DNA with C in mRNA
