NAME_____________________
LAB_________
DNA FINGERPRINTING: Who’s the father?
Background:
DNA fingerprinting is a way to determine the identity or relationships of people.
The technique is based on the fact that no two people, except identical twins, have
exactly the same DNA pattern or fingerprint. DNA fingerprinting has proved
useful in criminal identification, medical diagnosis, and research.
The following is a scenario about paternity determination.
In 1982, in the small town of Sebring, FL, an 8-pound baby boy was born. The boy’s
name was Anthony Ricci, born to Maria Ricci. The boy’s mother was unmarried and
listed no name under the heading of “father” on the birth certificate. Therefore
the child assumed under the same surname of his mother. Tony never knew his
father as he was gone before he was born, and his mother never spoke of him.
When asked, she told him that he was dead.
Tony grew to be a healthy, happy child. He loved his mother and his grandmother
(nana) with whom he lived. On June 12, 1989, on the way home from work, his
mother was hit by a drunk driver and was killed. Tony was only seven. His
grandmother went to court seeking guardianship so that he would not become a
ward of the state. It was granted.
Two years later, Tony’s grandmother purchased a lottery ticket. That week she
won a 5 million-dollar jackpot! They were able to purchase a new, larger home, and
other material items they could not previously afford. Unfortunately less than 6
months later, his grandmother past away from natural causes. Tony was left with
no guardian and a trust fund amounting to almost 4.5 million dollars. He was
instantly a celebrity. Newspapers all over America carried the headlines “poor,
rich, orphan seeks home”. Within three weeks the Sebring Department of Child
Services received notice that Tony’s father was here to claim him. THREE TIMES!
The first man, John McCarthy of Lakeville, Montana, claimed that he and Maria
had been engaged. Due to irreconcilable differences they parted ways. He claimed
she never told him she was pregnant, but by calculating back to their courtship he
deducted that the boy must be his.
The second man, Hugo Wile of Atlanta, GA, claimed that he and Maria had a long
relationship. Due to financial difficulties, he moved to GA to try a make his way.
He had promised to send for Maria when he was financially secure. That day never
came. Working as a construction worker, his pay was never steady enough to
support a wife, let alone a son.
The third man, Louis Vandercamp of New Orleans, LA claimed that he and Maria
had lived together for years. That after a major hurricane had destroyed their
home, Maria moved in with her mother while he stayed to rebuild. Since the
fishing industry was destroyed by oil spills (and he was a shrimp boat captain) he
never was able to get enough money together to rebuild their dream home. He just
never was able to face his family again after that.
Who do YOU think is the father?
Here is a letter from Anthony:
Dear Scientists,
I have a big problem. I don’t know who my dad is and I need your help. Here’s what
happened:
I was born in Sebring, Florida to my mom, Maria Ricci. Mom told me my dad was dead and that I
all I needed was her and Nanna. I kept asking her but she’d get really upset, so I stopped asking.
Then I was snooping around in her closet and found my birth certificate. My name and my
mom’s name are on it, but there’s a blank for my dad’s name. For a while, I wondered if I even
had a dad. After a while, I forgot about it, but then my mom was hit by a drunk driver on her
way home from work and died. Now I had no parents at all…I still had Nanna though and she
took really good care of me. She tried to make me feel better by making me my favorite
spaghetti and meatballs, but sometimes even that wouldn’t help. One day while we were out
shopping she told me that we’ve had enough bad luck in our lives and we should pray for some
change. So, she bought me a lottery ticket for my seventh birthday. That night we watched the
lottery drawing and you wouldn’t believe it, but we won!! We won 5 million dollars!!! I thought
Nanna was going to have a heart attack she screamed so loud! Later that month, Nanna
bought us a big, new house with a huge backyard, pool and swing set! She told me she was going
to put the rest of the money away in a trust fund for me for my education. For a while, we were
pretty happy. We even had a maid come in sometimes who cleaned my room. But then Nanna
started getting really sick. She was going to the doctor’s a lot and they put her in the hospital.
She died a month later. I really miss my mom and Nanna…And now I have another problem.
Since there isn’t anyone to take care of me, the newspapers did a story on me and about how I
have no family and all this money in a trust fund. Three people called the newspaper saying they
were my dad and that they were going to take care of me. I thought my dad was dead! My
foster family is saying that these men are “crackpots” and just want my money. But I really want
one of them to be my dad. I think I’d be nice to have a dad to build tree-houses with and go
fishing. Everybody else has a dad and since I have no mom or Nanna, maybe I should have a dad.
I just don’t know which one he is. Can you figure out if one of these men are my dad? It’d really
mean a lot to me. Thanks.
Anthony Ricci
Procedure:
1) You are given several DNA sequences from the following people:
-Tony’s mother (DNA sample from her femur bone)
-Tony (DNA sample from his blood)
-John McCarthy (DNA sample from his blood)
-Hugo Wile (DNA sample from his blood)
-Louis Vandercamp (DNA sample from his blood)
***Assume all DNA segments were taken from the same location on each person’s
chromosome #8
2) Cut out each person’s DNA and tape (or glue) it into a single line. You should
have four continuous pieces – one for each individual.
3) Now cut out several radioactive probes. Radioactive probes are known as
sequences of DNA (that is we know their base codes) because DNA is
complementary, the probes will attach themselves to their compliment. We are
using a probe that reads “GTA”.
What will this probe attach at?
4) Use tape and attach the probes at each complementary code on each person’s
DNA.
*Remember to indicate and keep track of which DNA strand belongs to whom!!
5) Line up Tony’s DNA fragment with that of his mother. You should note the
similarities between Tony’s DNA and that of his mother by writing an “M” on
each probe that indicates a match between Tony and his mom.
6) But Tony only gets half his DNA from his mother, and the other half from his
dad. You should now be able to see probes on segments that did not come from
his mother.
In order to determine who his real father is, find a match between Tony’s DNA
segments that did not match his mothers, and those of either Hugo and John.
Mark these segments with the first letter of the father’s name (either “J” “H” or
“L”)
QUESTIONS:
1) Who is Tony’s biological father? How do you know?
2) Why is it important that all four DNA sources were from the same chromosome
and the same location on each person’s chromosome?
3) What base sequence did the DNA probe GTA attach to? Why?
4) What does it mean when we say DNA is complementary?
5) We could have also used restriction enzymes in this lab, instead of probes.
Using what you learned in your last lab, explain how restriction enzymes would
have led us to the real father.
6) What are some other uses for this DNA fingerprinting technique?
7) Genetic profiles may become a routine part of medical check-ups in the not too
distant future. Explain why each from the list below should OR should NOT
have access to your DNA/ genetic records.
a)
b)
c)
d)
e)
you
your parents
the schools or colleges you attend
prospective employers
insurance companies