Download Dna sequence and Cell Activity

BLUEPRINT OF LIFE
HOW CHANGES IN DNA SEQUENCES CAN
ALTER CELL ACTIVITY – INVESTIGATION
Background Information
The sequence of bases on the DNA molecule provides a coded message for the manufacture of
proteins on the ribosome. Since many proteins manufactured are enzymes, a mutation or change in
this genetic code can have serious consequences for cellular metabolism. In the case of insertion or
deletion point mutations, for instance, the resulting protein is often non-functional and, if an enzyme,
can no longer control the metabolic reaction it is specific for.
Instructions
Read the following information and convert it into a flow chart using the headings provided as a
guide.
The code for a certain sequence of amino acids is located on a DNA molecule. It is CAG TAG
AGT TAA CGC. The corresponding transcribed code on a messenger RNA would be GUC AUC
UCA ACU GCG. The amino acids, carried by tRNA, that line up along this mRNA would be valine,
isoleucine, serine, threonine and alanine. These amino acids form part of a polypeptide that is the
basic unit of a particular enzyme. When synthesised, this enzyme will effectively mediate its own
specific cellular reaction.
Now, if the original DNA segment above undergoes a mutation in which the third guanine is deleted,
the new sequence will be CAG TAG ATT AAC GC. The transcribed mRNA code will now be
GUC AUC UAA UUG CG. The sequence of amino acids would still commence with valine and
isoleucine but it would finish here, because UAA is a `stop’ codon that directs the cell to release the
polypeptide that has formed. Polypeptides resulting from such deletion mutations are invariably nonfunctional and the metabolic reaction this enzyme is supposed to control will not take place.
Flow Chart
Cut out the flow chart components on the next page. Rewrite the table below into your books and
glue in the flow chart components in the appropriate places.
Normal protein
synthesis
Faulty protein synthesis
following mutation
Code (base sequence) on
original DNA
↓
Transcribed code on mRNA
↓
Sequence of amino acids
formed on ribosome
↓
Final polypeptide: functional
or non-functional?
↓
Cellular activity
proceeds/does not proceed
normally?
TITAN EDUCATION - BIOLOGY
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Flow Chart Components - cut out and paste in the correct positions in your book. Write the
appropriate information in the boxes.
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TITAN EDUCATION - BIOLOGY