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PERIOD
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Introduction
In humans, controlled crosses cannot be made, so geneticists must resort to scrutinizing family
records in the hope that informative matings have been made that can be used to deduce dominance
and distinguish autosomal from X-linked inheritance. The investigator traces the history of
some variant phenotype back through the history of the family and draws up a family tree,
or pedigree, using standard symbols. The clues in the pedigree have to be interpreted by a genetic
counselor. The genetic disorders of human beings can be dominant or recessive phenotypes and can
be either autosomal or X-linked. In this activity you will examine the pedigree of a family following
the occurrence of attached earlobes and construct a pedigree of a family with food allergies.
Pre-Lab
Tier 2: AWL Words
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Tier 3: Science Words
In your own words, why are human pedigrees useful?
Part I - Directions: Use your knowledge of genetics and pedigrees to answer the questions below.
Key:
Having floppy earlobes (FF or Ff) =
or
Having connected earlobes (ff) =
or
1. How many people are in the 3rd generation?
1.
2. Who is adopted?
2.
3. Who has died? (list all)
3.
4. Which 2 people are fraternal twins?
4.
5. How many brothers/sisters does Troy have?
5.
6. What is Denise’s genotype for earlobes?
6.
7. What is Gina’s genotype for earlobes?
7.
8. If Fred is hybrid for floppy earlobes and Gina
has connected earlobes, what is the probability
that Mike’s earlobes are connected?
8.
9. How are Lisa and Brad related?
9.
10. What happened to Chrissy and Nathan?
10.
11. What generation is Warren in?
11.
12. How is Luke related to Amy?
12.
Continued …
Part II - Directions: Read the passage below. On a clean sheet of paper, construct a pedigree that
represents the information below. Use a ruler (neatness counts) and create a thorough key of all the
symbols you use. (Hint – You may want to do a rough draft on some scrap paper, before
diagramming your final copy.)
Oscar and Natalie married and had 4 children: Brian,
James, Dawn, and Cindy. John and Louise married and
had 3 children: Beth, Brad, and Jake. Brad and Jake are
identical twins. Beth married James and had two
daughters: Peggy and Nancy. Brian married Susan and
they had a son, Tyler. Brian and Susan are now divorced.
Susan has remarried to Stanley. Susan and Stanley
adopted Tricia, their new daughter. Oscar, Dawn and
Louise are deceased.
In addition, research has been done on the family to trace
food allergies from generation to generation. Oscar, Brian,
and Cindy have/had a food allergy. Represent this on your
pedigree and use a key to show your work (i.e. green dots
= food allergy).