Preview - Central Dogma

Breaking the Rules

Return the free nucleotides to approximately 50 and make sure SUBSTITUTIONS is UNCHECKED. SETUP the simulation, press GO/STOP.

2. Unwind the DNA, separate the stands, attach the polymerase to the TOP strand ONLY. Observe the top strand of DNA, now.

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3. After the top strand is finished, turn SUBSTITUTIONS to ON and attach polymerase to the bottom strand. Observe replication of the bottom DNA strand.

4. Press GO/STOP to end the simulation.

5. Check the readout boxes for your top and bottom DNA strands (as in the picture below) by going to the Command center and typing in "calculate-mutations" then pressing enter

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Questions

Please answer the questions below.

Compare your top and bottom strands; what changed when you turned SUBSTITUTIONS on?  What do you think SUBSTITUTIONS means?

Hint:  You might want to compare this challenge to your results from Part 1 – Challenge 4.

Hint:  In order to see your DNA more clearly, press GO/STOP, change FREE-NUCLEOTIDES to zero, and move the enzymes out of the way, then press GO/STOP again!

What nucleotide pairings do you observe in the bottom strand but not in the top strand?

The changes you observed in the sequence of nucleotides in your DNA strand are called mutations.  There are several different types of mutations.  You simulated substitution mutations, meaning that some nucleotides were paired incorrectly during replication, for example a Thymine might be substituted where a Cytosine should be, or a Guanine substituted for an Adenine.  As a result, the two, new DNA strands that you made had different (mutated) sequences. 

What other kinds of mutations do you think might happen to change the sequence of nucleotides in DNA?

SAQ: The eumelanin and pheomelanin that give Lucy and Maria their hair colors are made by slightly different versions of the same protein.  Using information from this page and previous lessons, explain how these different proteins could come about.

Notes

These notes will appear on every page in this lesson so feel free to put anything here you'd like to keep track of.