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What do genes do?

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This free course, What do genes do? explores how information contained in DNA is used, explaining the flow of information from DNA to RNA to protein. Also introduced are the concepts of transcription (as occurs between DNA and RNA) and translation.

After studying this unit you should understand:

  • how the linear sequence of DNA within a gene is related to the linear sequence of amino acids of a protein
  • how the information in DNA is carried via RNA to make a protein
  • how RNA is synthesised from DNA by the process of transcription
  • where the processes of transcription and translation occur within the cell

By: The Open University

  • Duration 4 hours
  • Updated Monday 8th July 2013
  • Introductory level
  • Posted under Biology
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5 Where does transcription occur in the cell?

Up to now we have described the processes of transcription without considering where each occurs within the cell.

SAQ 5

Given that transcription — the production of mRNA — requires a DNA template, where do you think this process occurs in the cell?

Answer

It must occur in the nucleus where the DNA in the cell is located.

However, once mRNA is produced, it leaves the nucleus and protein synthesis – translation – occurs in the cytoplasm. Thus transcription and translation are separated both in space within the cell and in time, in that one occurs after the other, as shown schematically in Figure 11.8. Thus the role of mRNA is to carry a coded message from the nucleus where the information is stored, to the cytoplasm where the coded message is translated into a specific protein; hence it’s name – messenger RNA.

Translation occurs at particular sites within the cytoplasm; it occurs on ribosomes. Ribosomes are large aggregates of proteins and ribosomal RNA (rRNA). Hence three types of RNA are involved in the process of translation but only one of them, mRNA, codes for proteins.

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