Polymerase Chain Reaction Amplification
of DNA
Assignment: After listening to the in-class explanation of PCR, reading your background information and studying the diagrams provided, answer the following questions.
1. Briefly explain the steps involved in normal DNA replication
within a cell before mitosis.
2. What is the function of each of the following in a PCR reaction?
3. Briefly describe what the thermocycler (PCR machine) does and what happens in each of the following three steps of Polymerase Chain Reaction:
4. Suppose you start with one double-stranded molecule of DNA
and you want to amplify this one DNA molecule by PCR. You add an excess of a
two single-stranded primers, each of which will anneal to the DNA molecule in
only one place, copying the segment of DNA between them. Draw representations
of the DNA and primers in each of 3 cycles. Label the template DNA, the primers,
and the newly synthesized DNA strands. Show the direction of DNA synthesis on
each strand.
How many molecules of double-stranded DNA will you have after
three cycles? After six cycles? After 100 cycles?
5. Compare the normal process of DNA replication within a cell
to the artificial replication of DNA molecules in a PCR machine. Describe what
is different between these two processes.
6. What kinds of changes to chromosomes would cause a "polymorphism"
to appear in the DNA profiles of different individuals from a population?
How would a deletion in the chromosome of one individual cause
a band to run closer to the wells in a gel?