Lesson 3: DNA Transcription

Learning Goals:

• Compare and contrast DNA and RNA.

• Explain how the cell “reads” the code in DNA.

• Describe how transcription and translation allow cells to produce the proteins that allow life to function.

RNA

What is RNA?

RNA is a single stranded DNA
molecule that has three roles within
the cell:

1. Carry the coded message in DNA to the cell.

2. Carry amino acids that can be
   chained together to build proteins.

3. Build ribosomes, which are the protein factories in the cell.

Comparing RNA and DNA

• DNA and RNA are both nucleic acids.

• RNA is single-stranded, DNA is
  double-stranded.

• The sugar in RNA is ribose.

• RNA contains uracil (U) and not
  thymine (T). U replaces T.

• DNA is only found in the nucleus where RNA can be in or out of the nucleus.

Transcription

Transcripton is the process of transcribing (copying) the genetic
code in DNA into RNA.

DNA is too large to leave the nucleus so the code is copied or transcribed into RNA because it can go into the cell.

RNA polymerase, an enzyme attaches itself to a region of DNA called the promoter. It is a region right in front of a gene that is getting ready to be
transcribed.

It transcribes DNA into a molecule called messenger RNA (mRNA). mRNA carries the DNA "message" into the cell.

The mRNA then exits the nucleus into the cytoplasm.