Download Application of Pedigree Analysis

Pedigree Analysis- Annotate the following informational text on pedigree.
Use the symbols we have been utilizing this semester to annotate. Pull out 4
important points from the text and summarize them in the margins as well.
What is it ?
A pedigree is a diagram of family relationships that uses symbols to represent people and lines to
represent genetic relationships. These diagrams make it easier to visualize relationships within families,
particularly large extended families. Pedigrees are often used to determine the mode of inheritance
(dominant, recessive, etc.) of genetic diseases. A sample pedigree is below.
How is it organized?
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squares represent males
circles represent females.
Horizontal lines connecting a male and female represent mating.
Vertical lines extending downward from a couple represent their children. Subsequent generations
are therefore written underneath the parental generations and the oldest individuals are found at the
top of the pedigree.
If the purpose of a pedigree is to analyze the pattern of inheritance of a particular trait, it is customary to
shade in the symbol of all individuals that possess this trait In the pedigree above, the grandparents had
two children, a son and a daughter. The son had the trait in question. One of his four children also had the
trait.
Active Notes/ Cornell Style:- Create 5 questions that can be answers by reading the above selection.
Write the questions on the left and answers on the right.
In the exercises below, assume that the trait in question is a genetic disease or abnormality. We will learn
patterns of inheritance that have the following modes of inheritance:
autosomal dominant
autosomal recessive
X-linked recessive
Developing Conclusions About Different Modes of Inheritance
Autosomal Dominant?
Autosomal Recessive?
Answers
Answers
X-Linked Recessive?
MAKING A PEDIGREE CHART
Now, follow the story, and make the appropriate pedigree chart.
This is the story of Grandma and Grandpa Flipnob, and their clan! They were married way back in 1933,
and have been just like newlyweds ever since. From their union, 4 individuals were created. Elizabeth, the
eldest, was born in 1935. Fred soon followed in 1936. In 1939 Michelle was brought into this world.
Mickey (a surprise to the whole family was the baby of the family, not being born until 1950.
Elizabeth fell in love at a young age, and wed her high school sweetheart, David, in 1954. From this
marriage, two bundles of joy came about (at the same time):
John and Sonny - 1955 (twins)!
It took Fred a little longer to find his soul mate. Finally in 1970, Fred found the woman of his dreams,
Wilma, and they were married. Since they married so late in life, they only brought one new person into
this world:
Barney - 1972
Michelle was a hard working woman, and never found time in her schedule for love. She led a very
productive and fulfilling life, but she never did marry and have children.
Mickey was a wild one!! After a long string of girlfriends, he finally chose Monica to spend the rest of his
life with. They were wed in 1975 and brought two girls into this world:
Krista - 1977
Janet - 1979
Answer the following questions regarding your pedigree:
1. Who are the inlaws?
2. What is the relationship between the people in the third generation?
Now that you have your pedigree chart together, shade the appropriate circles and squared from the
information to follow. Remember that individuals who possess the RECESSIVE trait are to be filled in.
Those individuals not filled in possess at least one dominant trait.
Dominant/Recessive Inheritance - Freckles
Not having freckles is a recessive trait.
Grandpa Flipnob did not have freckles, but his beautiful bride did.
Fred and Michelle were the only two of their siblings to have freckles.
Of the grandchildren, the twins did not have freckles, and neither did Barney, but the two girls did.
Now: Using the guide provided, determine the genotypes of all individuals in this pedigree chart for
freckles. Remember, having no freckles is a RECESSIVE trait.
GUIDE
STEP 1
Assign two recessive genes to any person on the pedigree whose symbol is shaded. Small letters are
written below the persons symbol.
STEP 2
Assign one dominant gene to any person on the pedigree whose symbol is unshaded. A capital letter is
written below the persons symbol.
STEP 3
Use the information given to you to determine the second alleles for each person with the dominant
phenotype.
Example: We know that Grandpa Flipnob does not have freckles. If Grandma were BB, could any bb
children be produced from Grandma and Grandpa? If Grandma were Bb, could any bb children be
produced from them? Do Punnett squares below to determine your answer.
From your results, what is Grandma s genotype? ____________________
What must be the genotypes of their children? ____________ ____________
(2nd generation)
Fill in these genotypes (along with Grandpa s) beside the appropriate circles and squares.
Complete this process until the entire pedigree is completed.
Sex-Linked Inheritance - Colorblindness
To complete this part of the activity, you will need to make a copy of your pedigree chart. There is no
guide to go along with this section. Just remember to determine the genotypes of those possessing the sexlinked trait first. From there, using Punnett squares, you should be able to determine the genotypes of
most, if not all of the family.
Neither Grandma or Grandpa Flipnob are colourblind.
All of their children have normal colour vision, except for Mickey.
Of the grandchildren, the twins both inherited colourblindness, as did their cousins, Barney and Janet.
There still remains one colourblind person in this clan, however, that is up to you to determine who.
What are the genotypes of the individuals in the Flipnob family for colourblindness?
In the exercises below, assume that the trait in question is a genetic disease or abnormality. We will learn
patterns of inheritance that have the following modes of inheritance:
autosomal dominant
autosomal recessive
X-linked recessive
Developing Conclusions About Different Modes of Inheritance
Autosomal Dominant
1. The pedigree below is for a genetic disease or abnormality. We do not yet know if it is dominant or
recessive. We will determine if it is possible that the trait is autosomal dominant. If the trait were
dominant, we would use the following designations:
A = the trait (a genetic disease or abnormality, dominant)
a = normal (recessive)
If the trait were recessive, we would use the following designations:
A = normal (dominant)
a = the trait (a genetic disease or abnormality, recessive)
a) Assume for the moment that the trait is dominant (we don't know yet). The pedigree shows that three of
the individuals have the recessive (normal) phenotype and one individual has the dominant (abnormal)
phenotype. Write the genotype of the affected (abnormal) individual next to her symbol in the pedigree
below. If you only know one of the genes (letters), use a "?" for the unknown letter. If possible, write the
genotype of the three recessive individuals next to their symbols. As you attempt to write the genotypes,
keep in mind that the pedigree may not be possible for a dominant trait; it may not be possible to write the
genotypes.
b) Is it possible that the pedigree above is for an autosomal dominant trait?
c) Write the genotypes next to the symbol for each person in the pedigree below assuming that it is for a
dominant trait.
d) Is it possible that this pedigree is for an autosomal dominant trait
e) What can you conclude from these two examples about the parents of a child that has a dominant
characteristic? Put your answer to this question in the summary table (item #1) in the answer sheet.
2. We will determine if the pedigree below can be for a trait that is autosomal dominant. Use "A" and "a"
as you did for the pedigrees above.
a) Write the genotype of each individual next to the symbol.
b) Is it possible that this pedigree is for an autosomal dominant trait?
c) In conclusion, can two individuals that have an autosomal dominant trait have unaffected children? Put
your answer to this question in the summary table (item #2) in the answer sheet.
Autosomal Recessive
3. We will determine if the pedigree below can be for a trait that is autosomal recessive. Use the following
designations:
A = normal
a = the trait (a genetic disease or abnormality)
a) Assuming that the trait is recessive, write the genotype of each individual next to the symbol.
b) Is it possible that the pedigree above is for an autosomal recessive trait?
c) Assuming that the pedigree below is for a recessive trait, write the genotype next to the symbol for each
person.
d) Is it possible that this pedigree is for an autosomal recessive trait?
e) If a trait is autosomal recessive, what can you conclude about the children if both parents are affected?
Put your answer to this question in the summary table (item #3) in the answer sheet.
4. We will determine if the pedigree below can be for a trait that is autosomal recessive. Use "A" and "a"
as you did for the previous example.
a) Write the genotype of each individual next to the symbol.
b) Is it possible that this pedigree is for an autosomal recessive trait?
c) If a trait is autosomal recessive, what can you conclude about the children of two parents that are not
affected? Put your answer to this question in the summary table (item #4) in the answer sheet.
5. We will determine if the pedigree below can be for a trait that is autosomal recessive.
a) Write the genotype of each individual next to the symbol.
b) Is it possible that this pedigree is for an autosomal recessive trait?
c) In this pedigree, two generations have been skipped. What can you conclude about recessive traits
skipping generations (is it possible or not)? Put your answer to this question in the summary table (item
#5) in the answer sheet.
X-Linked Recessive
The conclusions that you made for autosomal recessive traits apply to X-linked traits. In this exercise, we
will work on some additional conclusions because males have only one X chromosome and females have
two.
6. We will determine if the pedigrees below can be for a trait that is X-linked recessive. Use the following
designations:
XA = normal
Xa = the trait (a genetic disease or abnormality)
Y = Y chromosome (males only)
a) Write the genotype of each individual next to the symbol.
b) Is it possible that the pedigree above is for an X-linked recessive trait?
c) Write the genotype next to the symbol for each person in the pedigree below.
d) Is it possible that this pedigree is for an X-linked recessive trait?
e) Write the genotype next to the symbol for each person in the pedigree below.
f) Is it possible that this pedigree is for an X-linked recessive trait?
g) Write the genotype next to the symbol for each person in the pedigree below.
h) Is it possible that this pedigree is for an X-linked recessive trait?
i) What can you conclude about the children of mothers affected with an X-linked recessive characteristic?
Put your answer to this question in the summary table (item #6) in the answer sheet.
7. We will determine if the pedigree below can be for a trait that is X-linked recessive. We will continue
to use the designations "XA and Xa".
a) Write the genotype of each individual next to the symbol.
b) Is it possible that this pedigree is for an X-linked recessive trait?
c) Which parent did the son get the Xa gene from?
d) What can you conclude about father-to-son transmission of X-linked traits? Put your answer to this
question in the summary table (item #7) in the answer sheet.
8. We will determine if the pedigree below can be for a trait that is X-linked recessive.
a) Write the genotype of each individual next to the symbol.
b) Is it possible that this pedigree is for an X-linked recessive trait?
c) What can you conclude about the children if both parents are affected with an X-linked recessive trait?
d) How does this conclusion compare with the one you made earlier if about both parents being affected
by an autosomal recessive trait?
e) Do the conclusions that you made for autosomal recessive traits apply to X-linked recessive traits? Put
your answer to this question in the summary table (item #8) in the answer sheet.
9a. If a genetic disease is X-linked recessive, what is the phenotype of a female that has only one disease
allele (Xa)?
b. What is the phenotype of a male with one disease allele?
c. What can you conclude about the number of males that would have the disease compared to the number
of females? Put your answer to this question in the summary table (item #9) below.
Application of Pedigree Analysis
The conclusions about inheritance (above) can be used to help analyze pedigrees. For each pedigree
below, tell if the trait can be autosomal dominant, autosomal recessive, and X-linked recessive. If the
pedigree cannot fit a mode of inheritance, tell why.
Pedigree A
Pedigree B
Questions 10 through 15- enter either "yes" or "no" in the table below.
Pedigree A
Autosomal dominant?
Autosomal recessive?
X-linked recessive?
10)
12)
14)
Pedigree B
11)
13)
15)
For each "no" in the table above, explain why or why not below. In your answers, refer to specific
individuals in the pedigree by number.
Pedigree A
Autosomal dominant
Autosomal recessive
X-linked recessive
Pedigree B