Unit 4, Lesson 15

 

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
    reading frame.

Lesson Outline
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
      http://www.johnkyrk.com/DNAreplication.html
     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. S ee an 
     animation of the process at 
     http://bcs.whfreeman.com/thelifewire/content/chp12/1202001.html
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://vcell.ndsu.edu/animations/translation/movie.htm  and
    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:
      http://learn.genetics.utah.edu/content/disorders/
    1. Deletion mutations - a base is removed from the sequence which alters the reading 
        frame.
    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.