Process Of Transcription Essay Topics


Transcription is the process by which a DNA sequence (gene) is copied into a complementary RNA sequence by RNA polymerase

  • Free nucleotides exist in the cell as nucleoside triphosphates (NTPs), which line up opposite their complementary base partner
  • RNA polymerase covalently binds the NTPs together in a reaction that involves the release of the two additional phosphates
  • The 5’-phosphate is linked to the 3’-end of the growing mRNA strand, hence transcription occurs in a 5’ → 3’ direction

Direction of Transcription

Overview of Transcription

The process of transcription can be divided into three main steps: initiation, elongation and termination

  • In initiation, RNA polymerase binds to the promoter and causes the unwinding and separating of the DNA strands
  • Elongation occurs as the RNA polymerase moves along the coding sequence, synthesising RNA in a 5’ → 3’ direction
  • When RNA polymerase reaches the terminator, both the enzyme and nascent RNA strand detach and the DNA rewinds


Many RNA polymerase enzymes can transcribe a DNA sequence sequentially, producing a large number of transcripts 

  • In eukaryotes, post-transcriptional modification of the RNA sequence is necessary to form mature mRNA

Summary of Transcription

Transcription Animation

Understanding:

•  Transcription occurs in a 5’ to 3’ direction

There are more than 200 different cell types in our bodies. The differences between cells in a multicellular organism arise differences in gene expression, not from differences in the cells' genomes (with the exception of antibody-producing cells).

During development, cells differentiate from each other. During this process, there are a number of regulatory mechanisms that switch genes on and off. As genes code for a specific protein, by switching genes on and off, the organism can control the proteins made by its' different cells. This is very important - you don't want a muscle cell secreting amylase, and you don't want your brain cells to start creating myosin. This regulation of genes is controlled by cell-cell comunications

This analogy may help: Imagine you are painting your house at night - you need lots of light so switch on all of the lights in your house. When you finish painting, you want to watch TV in the lounge. Your purpose has now changed and you want the lighting (gene expression) to suit your purpose. You have two options:

  1. Switch off the lights using light switches (change the gene expression)
  2. Shoot out the lights you don't need (deleting genes and mutating DNA)

Which one would you pick? It is safer to turn off the lights, even if you never want to turn it on again. By shooting out the light, you risk damage to the house; by deleting a gene you don't want, you risk damaging genes you do want.

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