Question

What do you understand by transcription? Describe it.

Hint:

Transcription is the first step in gene expression, where DNA is transcribed into mRNA. Remember, in RNA, uracil (U) replaces thymine (T).

Answer 1

Transcription is the process by which an RNA molecule is synthesized from a DNA template. It is the first step in the central dogma of molecular biology, where genetic information in DNA is used to produce a complementary RNA strand. The process of transcription occurs in three main stages:
1. Initiation:
The process begins when the enzyme RNA polymerase binds to the promoter region of the DNA. The promoter is a specific sequence of nucleotides that signals the start of a gene. RNA polymerase unwinds the DNA strands, exposing the template strand.
2. Elongation:
RNA polymerase moves along the DNA template strand, reading the sequence of nucleotides and synthesizing a complementary RNA strand. In this stage, RNA is built in the 5' to 3' direction, with RNA nucleotides (A, U, C, G) pairing with the complementary bases on the DNA strand (A pairs with U, and C pairs with G).
3. Termination:
Once RNA polymerase reaches a specific sequence called the terminator, the RNA transcript is released. The RNA molecule then detaches from the DNA, and the DNA strands re-anneal. The newly formed RNA molecule is called messenger RNA (mRNA) in eukaryotes and can undergo further processing before translation.
Key Points:
- Transcription is essential for protein synthesis, as it produces the mRNA, which carries the genetic code from DNA to ribosomes for translation.
- In eukaryotic cells, transcription occurs in the nucleus, while in prokaryotes, it occurs in the cytoplasm.