Page 10 - CH6 (1)

open, but a small opening forms in which replication occurs. This small
opening forms a replication fork.

● DNA polymerase can polymerise only in one direction that is ' ​​
.

● Therefore, replication occurs smoothly at to end of DNA.

(continuous replication, but occurs discontinuously at to end)

● The discontinuous fragments so formed are joined by DNA ligase.

Transcription Unit ­­­ Structure and its Relationship with a Gene

Transcription

● Transcription is the process of formation of RNA molecules from the
DNA.

● During transcription, only a segment of DNA from only one of the
strands participates.

● Both strands are not copied during transcription because:
○ If both strands get transcribed at the same time since the

sequences of amino acid would be different in both (due to
complementarity), then two RNA molecules with different
sequences will be formed, which in turn give rise to two different

proteins. Therefore, one DNA would end up giving rise to two
different proteins.

○ Two RNA molecules so formed will be complementary to each
other, hence would end up forming a double­stranded RNA
leaving the entire process of transcription futile.