Lesson 15 - Taking a Deeper Look at Cellular Nucleic Acids and their Functions
Student Performance Objectives
1. Explain DNA replication.
2. Compare DNA replication with DNA's transcription of a message to m-RNA.
3. Describe translation utilizing the following terms: ribosome, m-RNA, t-RNA's, amino acids,
codons and anticodons.
4. Define mutation and describe the effect of a deletion or substitution mutation on the m-RNA
A. DNA is a most remarkable molecule with the ability to make exact copies of itself, a process called
replication and clearly important for the continuation of life from generation to generation. Read about
this at the following website:
1. DNA replication is semiconservative. To see what this means go to
http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/REP/DR.Semi.html Also see
2. DNA codes for the synthesis of proteins. To get an overview of this process, go to
http://www.johnkyrk.com/DNAtranscription.html for a more detailed view.
B. The DNA molecule, in the cell's nucleus, sends a messenger molecule to the ribosomes,
located in the cell's cytoplasm, to begin the process of protein synthesis. The messenger
molecule formed is called messenger RNA. Its formation is called transcription. See an
animation of the process at
C. The messenger RNA molecule, interacting with the ribosomes can take part in the synthesis
of proteins, a process called translation.
D. Animations of the process of translation may be found at
http://www.johnkyrk.com/DNAtranslation.html which is very detailed but revealing.
F. The occurrence of a mutation changes the sequence of bases in a DNA molecule. This
changes the sequences of bases on a messenger RNA molecule transcribed from the mutated
DNA molecule. The resultant protein synthesized from the translation of this m-RNA
molecule will have an altered sequence of amino acids. This protein might function normally,
might function suboptimally, or might not function at all. Read more about mutations at:
1. Deletion mutations - a base is removed from the sequence which alters the reading
2. Substitution mutation- one base is substituted for another. The reading frame is not
altered but the codon containing the substituted base is not different and may code for
a different amino acid than the original.