Transcription
Home Up Transcription Translation Replication Review of Processes

 

Transcription

How do we get from DNA molecules to protein molecules?

First, a portion of the DNA molecule is split.

Portion of DNA molecule being split. [69042.jpg]
Then with the help of an enzyme, another molecule, an RNA molecule, ribonucleic acid molecule is formed. Specifically, it's called a messenger RNA molecule (mRNA).

The way that this is formed is that, with the help of an enzyme, next to each base in the DNA is placed the complementary RNA base with its appropriate sugar (ribose) and phosphate. Next to each adenine is a uracil. Next to each cytosine is a guanine. Next to each guanine is a cytosine. Next to each thymine is an adenine. These nucleotides are then bonded to one another. In this way, a messenger RNA molecule is made in a sequence that's dictated by the sequence of bases in the DNA molecule.

Complementary m-RNA molecule next to one strand of DNA. [69043.jpg]
The messenger RNA molecule moves away and the DNA molecule closes back together.  This is the process called transcription.

mRNA separated from DNA. [69044.jpg]

Practice

Draw the segment of mRNA that is complementary to the top strand of the DNA segment shown here. Use the abbreviations P, R (ribose), D (deoxyribose), U, T, A, C, G in your diagram. Check your answer below. Keep your answer handy for use in the following sections.

     -P-D-P-D-P-D-P-D-P-D-P-D-P-
        |   |   |   |   |   |
        C   T   A   G   C   T

        G   A   T   C   G   A
        |   |   |   |   |   |
     -P-D-P-D-P-D-P-D-P-D-P-D-P-

Answer

        G   A   U   C   G   A
        |   |   |   |   |   |
     -P-R-P-R-P-R-P-R-P-R-P-R-P-

 

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E-mail instructor: Sue Eggling

Clackamas Community College
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