Transcript H? - Cloudfront.net

A pedigree is a chart for tracing genes in
a family.
• Phenotypes are used to infer genotypes on a pedigree.
• Autosomal genes show different patterns on a pedigree than sex-linked
genes.
• Ex:
Creating a pedigree
• Okay, here are some general rules to keep in
mind when creating a pedigree:
1. Circles are used to represent females
2. Squares are used to represent males
3. Circles/squares are filled in when a certain trait
or disorder is expressed.
4. Circles/squares are half shaded or dotted to
represent carriers (heterozygous individuals).
Note: Carriers of recessive diseases/disorders are
considered HEALTHY and don’t express the disease or
disorder. So, often, when someone is healthy, we don’t
know if they’re homozygous or heterozygous. Unless, of
course, the disease/disorder is dominant.
Creating a pedigree (cont.)
• Let’s try an example (create your pedigree on a
separate sheet of paper [for practice], following these
instructions; you only have to include the actual
drawing):
Trace the Ramirez family history of PKU
(phenylketonuria), which is a recessive
genetic disorder (healthy is dominant).
1. Lets start with a key:
H = Healthy
h = PKU
Creating a pedigree (cont.)
2. Manny and Rosa are married and both
are healthy.
So…we draw an open circle and a square connected:
Creating a pedigree (cont.)
3. They have 3 children.
4. Their oldest child, Jacob, has a recessive
disorder called PKU. So, we draw a filled in square.
Creating a pedigree (cont.)
5. Their middle child Erica and their youngest
Matthew are healthy. We draw an open circle and square.
6. Now, If healthy is dominant to PKU, fill in
the missing genotypes. (start with what you
know).
Creating a pedigree (cont.)
• We know Jacob has PKU, so he is hh.
hh
• Now, work backwards for the rest…
If Jacob is hh, then he has to have gotten one of each allele from
each parent.
H
h
Since Manny and Rosa are
healthy, it is safe to say
they are heterozygous.
H
h
hh
Creating a pedigree (cont.)
• By finishing the punnett sqaure, we know that
the other 2 children could be either homozygous
dominant or heterozygous.
H
h
• You should have something
H HH Hh
like this…
Hh
hh
Hh
H?
h Hh
H?
hh
The next generation
• Now lets add on to this…
7. Erica meets Moe in college and the two
become married (add to your pedigree).
8. Erica and Moe have 2 daughters (add this
to your pedigree).
9. Their youngest daughter, Jaime, shows
signs of PKU, while Aimee does not (add
to pedigree).
10. Fill in the genotypes of the four
individuals…starting with what you know.
The Next Generation
Key
H = Healthy
Hh
Hh
h = PKU
H?
hh
This is what you should
have! Woo-hoo!
(Mrs. Moore)
Sickle cell anemia (recessive) pedigree
Use the key and fill out this pedigree (you can write on this)
Hint: 3 unknown
Key
H = Healthy
h = Sickle cell anemia
You should have something that looks like
this…
Hh
H?
hh
hh
Hh
hh
Hh
Hh
hh
Hh
Hh
H?
Key
H?
H = Healthy
h = Sickle cell anemia