Free online lectures of Biochemistry for medical and allied students by the Biochemistry Club
Transcription
- Transcription can take place at any time but only certain selected regions of the DNA are copied. This is like taking xerox copy of particular page of the book.
- The genetic information in DNA is transcribed (copied) to the messenger RNA (mRNA).
- During transcription, the message from the DNA is copied in the language of nucleotides (4 letter language).
- The mRNA then reaches the cytoplasm where it is translated into functional proteins.
- During translation, the nucleotide sequence is translated to the language of amino acid sequence (20 letter language).
- Q: What is the name of the enzyme that performs this action?
- A: RNA Polymerase (RNAP).
- Q: What it does?
- A: RNA Polymerase adds nucleotides (ATP, UTP, CTP, GTP) to make a strand of RNA that is complementary to DNA.
- Q: What is the Direction of synthesis?
- A: It is always from 5’ to 3’.
- Q: Only one strand is copied – which one?
- A: Template strand (non-coding, anti-sense strand).
- RNAP reads the template strand & synthesizes RNA that is identical to coding strand except it has ‘U’ instead of ‘T’.
- Q: How does RNAP know where to begin transcribing?
- The PROMOTOR sequences on DNA determines the start sites for RNAP.
- RNAP has high affinity for them.
Facts about Transcription
- All of the DNA is NOT transcribed.
- RNAP initially finds and binds to the promoter, not the coding region.
- Gene = dsDNA; but only one strand is used as template for transcription i.e. the template strand & is complementary to mRNA.
- Coding strand is NOT used but is identical to mRNA (T replaces U) & has TATA sequence (CAAT box).
All these lectures are organized and listed in detail in their proper sections. To view these lessons please visit the Genetics Section. This can be approached by directly clicking the Biochemistry II button or it can also be approached from the drop down menu in Biochemistry II tab. Once you reach the section click the curriculum tab to view the full list in the section.
Any further questions or inquiries are welcome.