Discussion Assignment #8


This week we're taking a look at mutation. This one should be easy--just a basic fact-finding mission. A mutation is a permanent change in the genetic information (DNA). That's a fairly broad description, so this week you're going to explore some of the variations in that category of mutations called point mutations.

First task: What are point mutations and gross mutations? We need definitions and some examples of each. What are forward mutations and reversions? And here's the toughest one: Explain how it's possible for a gene's function to be restored without a true reversion.

Second task: What is a base substitution? Base substitutions come in two basic categories: transitions and transversions. What are these? If you have the following DNA sequence (one side of the DNA only shown), and a transition mutation occurs at the seventh base pair (remember, the partnering side is implied, but not shown--be sure you understand what "base pair" means), how will the DNA sequence be altered? What if you have a transversion mutation at that location?

DNA Sequence: A T G G T A C T T T C G C G A A C A G T C C C T T A G

Finally, what is a frame shift mutation? Using our same DNA sequence, and again involving that seventh base and its partner, write out the sequences of two different kinds of frame shift mutations. Briefly describe each one (in other words, what did you do to the sequence) after you write the altered sequence.

Now consider the following sentence:


Assuming that this sequence is like the base sequence of a gene, how would a base substitution mutation in the fourth letter affect the sense of the sentence? The mutation in this case will replace the "c" with a "b."

Again, going back to the original sentence, perform a deletion-type frame shift mutation involving the same letter. For the sake of this exercise, note that all words in the sentence must be three letters long. You are deleting only one base.

What conclusion do you draw about the degree of effect of point mutations vs. frame shift mutations?

Back to Discussion Assignment Index