Download Pedigrees - sciencewithskinner

Provided by: Tracie Schroeder; modified by Michel Skinner
Human Pedigree
Name __________________________
A diagram showing the transmission of a trait through several generations of a family is called a
pedigree. In Figure 1, generation I is made up of grandparents, generation II is their children, and
generation III is their grandchildren.
Study the pedigree diagram in Figure 1 to learn the symbols.
Female without trait
Male without trait
Female with trait
Male with trait
Female, died in infancy
Male, died in infancy
Identical twins
FIGURE 1
I
1
2
II
1
III
2
3
4
1
2
5
3
Provided by: Tracie Schroeder; modified by Michel Skinner
Individuals who lack an enzyme needed to form the skin pigment melanin are called albinos. Normal
skin pigmentation is dominant.
Use D to represent the gene for normal skin and dd to represent the genotype for
albinism. Where you cannot be sure whether an individual with the dominant trait is
heterozygous or homozygous, show the genotype as D-.
FIGURE 2
Genotype
I 1 ________
2 ________
3 ________
4 ________
II 1 ________
2 ________
3 ________
4 ________
5 ________
6 ________
7 ________
III 1 ________
2 ________
1. In the pedigree above, if individuals 6 and 7 have another child, what is the chance that it will be
an albino? ____________________________________________________________
2. Are individuals 1 and 2 in generation I homozygous or heterozygous? Explain.
______________________________________________________________________________
3. What gender is individual 3 of generation II? ____________________
4. What relationship do individuals 6 & 7 of generation II share? _____________________________
5. If Individual 2 of generation III married a man who was homozygous for normal skin, what would
be the probability of them having an albino child? _________________ What chance do they have
of having a girl? _____________ Draw their daughter in the pedigree.
Provided by: Tracie Schroeder; modified by Michel Skinner
Individuals who can taste the chemical phenylthiocarbamide, PTC, have the dominant gene, A.
Those with the recessive genes, aa, cannot taste it. Remember: People with the trait are shaded.
Use “A” to represent the gene for a PTC taster, a dominant trait. Use “aa” for the PTC
nontaster, the recessive trait.
FIGURE 3
Genotype
1 ________
2 ________
3 ________
4 ________
II 1 ________
2 ________
3 ________
4 ________
5 ________
6 ________
7 ________
8 ________
III 1 ________
2 ________
3 ________
4 ________
I
1. In the pedigree above, if individuals 4 and 5 in generation II have another child, what is the
probability that it will be a taster? _______________________________________
2. If individual 8 in generation II married a man with genotype AA, what is the probability that she
will have a non-taster child? _____________________________________
3. What relationship do individuals 4 & 5 of generation 2 from Figure 3 have? ________________
Homework: On a separate sheet of paper: Construct a pedigree diagram of your family for one
of the traits listed below. Pick a trait that is not found in all the members of your family. List as
many genotypes as possible. It should include your grandparents, parents and siblings. (3
generations)
Tongue rolling: Dominant trait; Non tongue rolling: recessive trait
Hitchhikers thumb: recessive trait; straight thumb: Dominant trait
Widow’s peak: Dominant trait; straight hairline: recessive trait
Attached earlobe: recessive trait; Free hanging earlobe: Dominant trait
Dimples: Dominant trait; lack of dimples: recessive trait
Provided by: Tracie Schroeder; modified by Michel Skinner
The Ultimate Pedigree Challenge
Is it possible for someone to be his own grandpa? This story is actually a song
written by Dwight Latham and Moe Jaffe (1947, General Music Publishing
Company, Inc.) Read the story (sing along if you dare) and draw the pedigree of
this man's family. GOOD LUCK!
Many, many years ago when I was twenty-three
I was married to a widow who was pretty as could be.
This widow had a grown-up daughter who had hair of red.
My father fell in love with her and soon the two were wed.
This made my dad my son-in-law and changed my very life
For my daughter was my mother, 'cause she was my father's wife.
To complicate the matter even though it brought me joy
I soon became the father of a bouncing baby boy.
My little baby then became a brother-in-law to dad
And so he became my uncle though it made me very sad
For if he is my uncle then that also makes him brother,
To the widow's lovely daughter who, of course, was my step-mother.
Father's wife then had a child which kept them on the run,
And he became my grandchild, 'cause he was my daughter's son;
My wife she is my mother's mother and it makes me blue,
Because although she is my wife, she's my grandmother too.
Now if she is my grandmother than I'm her grandchild
And every time I think of it, it nearly drives me wild;
For now I have become the strangest case you ever saw
As husband of my grandmother I am my own grandpa.
Chorus:
Oh, I'm my own grandpa, I'm my own grandpa
It sounds funny, I know, but it really is so
Oh, I'm my own grandpa.
Now see if you can create a pedigree for the narrator’s family!