Biology 12 Name: DNA Replication Worksheet DNA replication - use your DNA kit and follow the directions to replicate (duplicate) DNA. 1. Use your DNA kit and build the following section of DNA. Notice that you have been given only 1/2 of the DNA molecule so you will have to use yellow nucleotides to complete the DNA. A T A T A C G C G T A G C G A T A G C G A T A G C G (blue nucleotides) 2. In order for a cell to replicate its DNA it must have a supply of free floating nucleotides in the nucleus. Make sure you have plenty of yellow and blue nucleotides before starting. 3. Special enzymes (proteins) in the cell unzip DNA by breaking the hydrogen bonds between base pairs. Acting as one of these enzymes, unzip your DNA now. 4. Free floating nucleotides attach to each 1/2 of the DNA ladder and the nitrogenous bases form hydrogen bonds with the complementary base on the original strand. Perform this job for your cell now. Pay particular attention to complementary base pairings. 5. The last step in DNA replication involves connecting phosphate (P) to deoxyribose sugar (D) to form the sugar- phosphate backbone of each DNA strand. 6. If you have performed these steps correctly you should now have 2 identical strands of DNA. 7. All of the DNA found in humans is called the human genome. You may have heard that the human genome has now been mapped (determined) and it is estimated that there are about 3 billion bases in this human genome. Therefore, during replication an error rate of only 1 error per million bases would still yield 3000 mistakes or mutations. Fortunately, each cell has special enzymes to “proof read” and correct mistakes during DNA replication. Go back and proof read your DNA strands to make sure there are no mistakes during replication. 8. These proof reading enzymes are capable of “snipping out” errors in the DNA and replacing them with the correct nucleotide. Do this now if it is necessary. 9. Review DNA replication by viewing the animation: DNA replication and cell division Discussion questions: 1. Under each diagram, summarize the 3 steps required to replicate DNA. 2. What is the result of DNA replication? 3. Why would a cell be required to replicate its DNA? (be precise). 4. What does the phrase “complimentary base pairing” mean? 5. DNA replication is often referred to as a semi conservative process. What does this mean?