Download READING PEDIGREES

Name: ______________________________
TOC:_____
READING PEDIGREES
1. The following pedigree shows a family of Labrador retrievers from which your new pet
puppy has come from. Identify the genotypes of as many of the dogs as you can. There
may be some that you cannot determine due to lack of information. “Y” causes yellow fur
and “y” causes black fur. The circles represent females and
STEPS TO SOLVING A
the squares represent males. Darkened individuals on this
PEDIGREE
pedigree are recessive and so have the recessive black fur.
1.
Label all individuals as male or
All of the other individuals that are not filled in have yellow
female
fur. A recessive trait such as black fur can skip generations.
2. Label the phenotype
3.
= black fur/male
= yellow fur/male
= black fur/female
= yellow fur/female
4.
5.
6.
Identify the individuals with a
recessive trait. They must be
“bb”.
Identify dominant individuals.
They must all have at least a
single “B”.
Trace the recessive genes back
from the recessive individuals.
Place a “?” if you cannot
determine a genotype.
P
F1
F2
Your Puppy!
Name: ______________________________
Creating Pedigrees, Practice:
TOC:_____
Directions: For each of the following scenarios create a pedigree.
Include:
● The names of each family member
● A key to distinguish the phenotype of each
● The genotype of each family member
family member
● Answers to any questions
Note: Just as the Simpson’s family is fictional, so are these example traits. These traits, in reality, are not
inherited in a simple dominant/recessive manner.
Scenario 1:
Homer Simpson has a very large forehead, so does his
father. Marge Simpson, despite her large hair, has a
small forehead. Of their children, Bart, Lisa and
Maggie, only Bart has a large forehead. Large
forehead is the dominant trait.
Create a pedigree table including the 5 family
members described and Homer and Marge’s
parents. (if you know a family member has the
dominant allele and you don’t know if they are
homozygous or heterozygous write a “?” next to
the dominant allele, for example H?)
Scenario 2:
Milhouse van Houten has a round nose. Milhouse
thinks that he must have been given to the wrong
parents in the hospital because both of his parents and
his little sister, Milcasa, have stubby noses. At the last
van Houten family reunion Milhouse noticed that his
grandmothers both have stubby noses but that his
grandfathers both have round noses.
Assuming that Milhouse was not given to the
wrong parents in the hospital create a pedigree
table including the 8 family members described.
Is having a stubby nose trait dominant or
recessive? How can you tell?
Scenario 3:
Lisa, Bart and Maggie all have spikey hair. Their
mother Marge has curly hair, not spikey hair. An old
Scenario 4:
Marge and her sisters all have blue hair (her sisters’,
Selma and Patti, hair have gone prematurely gray from
Name: ______________________________
family photograph showed that Homer and his father
both had curly hair when they were younger. The same
photo shows that Homer’s mom had curly hair.
Create a pedigree table including the 7 family
members described.
Is spikey hair dominant or recessive?
If Bart married someone who was
heterozygous for curly hair what would be the
phenotypes of their children?
TOC:_____
years of cigarette smoking!) Homer had peach hair
(when he had hair.) All of Marge’s children have
peach hair. Marge has noticed that blue hair can skip a
generation since neither of her parents had blue hair.
Create a pedigree table including the 7 family
members described.
Is the peach or blue allele dominant?
Can you predict the genotypes for Marge’s
parents? (You do not need
to included them on the pedigree.)
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Interpreting Pedigrees Using Sex-Linked Genes
Directions: Recall that genes present on the X or Y chromosome are called “sex-linked” genes. Examine the pedigree
below that traces the sex-linked condition of rickets, which is caused by a dominant allele present on the X chromosome,
through 3 generations of a family. Use the information presented in this pedigree to complete the procedures and answer
the questions below.
Name: ______________________________
TOC:_____
Procedures:
1. Use your knowledge of genes, alleles and inheritance to determine the genotype of each individual represented in
the above pedigree. Write each individual’s genotype directly below the number (#) labeling each person.
Individual #2 has been labeled for you.
2. Answer the Analysis Questions below.
Analysis Questions:
1. What is the genotype of the parent (P) generation female?
2. What is the probability of the parent (P) generation female passing the rickets allele to the offspring (F1) generation?
3. What is the probability of the parent (P) generation male passing the rickets allele to the offspring (F1) generation?
4. Individual #8 has rickets. However, none of his 3 sons express this condition in their phenotypes. What accounts for
this?
5. What is the genotype of individual #4? Explain how you determined this.
6. Why is individual #11 free of the disease although his brother and sister do have it?