Biology · Molecular Basis of Inheritance · NEET
Transcription means copying the genetic information from one strand of DNA into RNA. The DNA stays inside; only a short RNA copy of the needed gene is made. This is the textbook NCERT definition and NEET has directly asked it as a true statement (NEET 2023): "The process of copying genetic information from one strand of the DNA into RNA is termed as transcription."
Transcription is DNA to RNA only. It is the first step. Making protein from that RNA is a different step called translation (RNA to protein). Do not mix them: Transcription = DNA to RNA, Translation = RNA to Protein. This order (DNA to RNA to Protein) is the central dogma.
The enzyme is DNA-dependent RNA polymerase. It uses DNA as the template and joins RNA nucleotides. NCERT also says this same enzyme opens (unwinds) the DNA helix during transcription. NEET 2020 asked "Name the enzyme that facilitates opening of DNA helix during transcription" and the answer is RNA polymerase, not helicase (helicase works in replication).
Two reasons given in NCERT. First, if both strands were copied they would make two different RNAs coding for two different proteins, which would confuse the cell. Second, the two RNAs would be complementary and stick together, forming a double strand that cannot be used to make protein. So only one strand acts as the template.
The RNA is chemically RNA (it has ribose sugar and uracil), but its base sequence copies the DNA. RNA polymerase can only add bases in the 5' to 3' direction, so it reads the DNA strand with 3' to 5' polarity (the template strand). The RNA it makes has the same sequence as the other DNA strand (the coding strand), just with U instead of T.
In eukaryotes, transcription happens inside the nucleus (where the DNA is). The RNA is then processed and sent to the cytoplasm for translation. In prokaryotes (bacteria) there is no nucleus, so transcription and translation can happen together in the cytoplasm.
Statement I: The process of copying genetic information from one strand of the DNA into RNA is termed as transcription. Statement II: A transcription unit in DNA is defined primarily by the three regions in the DNA, i.e., a promoter, the structural gene and a terminator. In the light of the above statements, choose the correct answer.
Name the enzyme that facilitates opening of DNA helix during transcription.
DNA-dependent RNA polymerase catalyzes transcription on one strand of the DNA which is called the:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Transcription is copying the genetic information from one strand of DNA into RNA, done by DNA-dependent RNA polymerase.
DNA-dependent RNA polymerase. In bacteria a single RNA polymerase makes all RNA types; in eukaryotes there are three (RNA polymerase I, II and III).
Transcription is DNA to RNA (making an RNA copy). Translation is RNA to protein (reading the RNA to build a protein). Transcription comes first.
It is a high-yield topic from Molecular Basis of Inheritance. NEET asks the definition, the enzyme, the one-strand logic, and template vs coding strand almost every year.
No. In the RNA made by transcription, uracil (U) takes the place of thymine (T). So where DNA has A-T, the RNA copy has A-U.
