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Title the next page of your composition notebook DNA Online Activity. Follow the instructions to complete the extension activity on DNA. Write the answers to the questions in your composition notebook. You do not need to write the questions.
PART 1- MITOCHONDRIAL DNA
Did you know you have a second set of DNA? It is the DNA found in your mitochondria.
1. Visit the Nature.com's page on Mitochondrial DNA and write down 5 ways that mitochondrial DNA (mtDNA) is different from the DNA found in the nucleus of cells.
Visit https://en.wikipedia.org/wiki/Mitochondrial_DNA.
2. If you were a plant, you would have a third set of DNA. What other organelle also has its own DNA?
3. From which parent does a person inherit their mitochondrial DNA?
Mitochondrial DNA is very helpful in tracing the ancestry of a person. Read about "Mitochondrial Eve" at NOVA Online and answer the following questions.
4. Who is (mitochondrial) "Eve?"
5. How many mitochondria are in each cell?
6. How many genes are in mtDNA?
7. What happens to the mtDNA from the sperm at fertlization?
8. What do researchers examine in the mtDNA which has allowed them to create a universal family tree?
9. According to the article, when did the most recent common ancestor of humans and
Neanderthals live?
PART 2- FORENSIC DNA; Solving a Bank Robbery
Figure 1 is an example of DNA patterns made by gel electrophoresis derived from a DNA database. A series of bank robberies took place in one town during the past 4 days. Your job will be to determine if the robberies were linked and if any of the suspects now in custody are the guilty parties.
Evidence #1- The First National Bank was robbed at noon on Monday. The bank robber ran up to the drive-through window and demanded money. The robber made off with an unspecified amount of money, but cut a finger smashing the surveillance camera. Police detectives analyzed the blood sample. The DNA sample is the sample shown in the first column in Figure 1. It is labeled Bank 1.
Evidence #2- The Second National Bank was robbed at 11 A.M. on Tuesday. This time the robber entered the bank and handed the teller a note demanding an unspecified amount of money. The teller handed over the money but kept the envelope. Luckily for detectives, the robber licked the envelope, leaving behind a DNA sample. It is possible that some of the teller's DNA could also be found on the envelope as she did handle the envelope. This sample can be found in the second column of Figure 1. It is labeled Bank 2.
Evidence #3- The Third National Bank was robbed at 10 A.M. on Wednesday. The robber demanded money and left without leaving any evidence at the teller's station. However, the robber had been chewing gum and, just before stepping up to the teller, dropped the gum in the trash can. Observant witnesses alerted police and the gum was collected and analyzed. DNA was extracted and this sample is seen in the third column of Figure 1. It is labeled Bank 3.
10. Does it appear that any of the bank robberies were committed by the same person? Explain.
11. Which suspect would you bring in for further questioning?
12. What bank (s) does it appear that they robbed?
13. How can you determine which bank the employee worked at simply be examining the DNA?
14. What advice would you give detectives regarding the suspects tested and Bank 2?
PART 3- FORENSIC DNA; The Royal Romanov Family
On July 16, 1918, members of the Romanov royal household- Tsar Nicholas III of Russia, his wife, the Tsarina Alexandria, their five children, their family doctor, and three servants- were secretly executed by a Bolshevik firing squad and buried in an undisclosed location. Eyewitness accounts by members of the firing squad stated that shortly thereafter, the bodies of two children were removed from the burial site and cremated.
In 1991, nine skeletons were exhumed from a shallow grave near Ekaterinburg, Russia. Physical characteristics of the skeletons revealed that three of the skeletons belonged to female children; two were from adult females; and four were from adult males. Nuclear DNA samples from the skeletons were taken and compared to determine relatedness among them.
The table below shows the five genetic markers that were analyzed for comparison.
Look at the DNA markers of the children and compare them to those of the adults. Remember that the offspring get half of their DNA from their mother and half from their father, and assume that the three children share the same parents.
15. Determine which two adults could have been the parents of the children. EXPLAIN your conclusions.
Investigators hypothesized that the remains of five individuals were those of the royal family, while the rest belonged to the doctor and servants. To support their hypothesis mitochondrial DNA from each female skeleton was compared to that of the Tsarina Alexandria's closest living maternal relative- Prince Philip, Duke of Edinburgh, whose grandmother was the tsarina's sister. A the same time, mtDNA from male skeletons was compared with that of Tsar Nicholas II's closest living relative- his great grandnephew James, the Duke of Fife.
16. Compare the simulated DNA sequences in both of the following tests, looking for differences in bases. Do they support the hypothesis that skeletons 3 and 8 are from the tsar and his wife? Explain your answer.
17. To further confirm the identity of skeleton 3, the body of the tsar's brother Georgij Romanov was exhumed and mtDNA was sampled. As expected, Georgij's mtDNA was a match. Consider the four tests that were performed and summarize how the evidence suggests that the skeletal remains found at Ekaterinburg belong to the murdered Romanovs.
18. Anna Demidova, Tsarina Alexandra's lady-in-waiting, was among those household members murdered in 1918. Can you presume that skeleton 9 is hers? Explain what type of testing you might do to provide conclusive evidence.
Extension:
If you have time, watch the National Geographic video The Mystery of the Romanovs
