How are RNA bases freed up during transcription to form base pairs?

During transcription, the process of transcribing DNA into RNA, RNA bases are freed up to form base pairs through the action of an enzyme called RNA polymerase.

Here's how it happens:

1. Initiation: RNA polymerase binds to the DNA molecule at a specific region called the promoter sequence. The promoter sequence helps in initiating the transcription process. Once the RNA polymerase is bound, it starts unwinding the DNA helix locally.

2. Elongation: As the DNA helix unwinds, the RNA polymerase moves along the DNA strand, synthesizing the RNA molecule in the 5' to 3' direction. The enzyme adds complimentary RNA nucleotides to the growing RNA molecule, following the base-pairing rules: adenine (A) with uracil (U), cytosine (C) with guanine (G), guanine (G) with cytosine (C), and thymine (T) with adenine (A).

3. Base pairing: As the RNA polymerase moves along the DNA strand, it exposes a segment of the DNA molecule, called the template strand. The RNA polymerase reads the template strand and uses it as a guide to synthesize a complementary RNA strand. For example, if the DNA template strand has an adenine (A), the RNA polymerase will add a uracil (U) to the growing RNA molecule. This process continues until the RNA polymerase reaches a termination sequence.

In summary, during transcription, RNA bases are freed up by the action of RNA polymerase. The enzyme unwinds the DNA helix, exposes the template strand, and adds complementary RNA nucleotides to synthesize a new RNA molecule. The base-pairing rules between DNA and RNA nucleotides guide the synthesis of the RNA strand.