Heredity Teachable Unit:
Mendelian Inheritance
Group 6: HHMI SI, 2011, Yale University
Bob O’Donnell and Kevin Militello (SUNY Geneseo)
Cintia Hongay and Jim Schulte (Clarkson)
Anne Dranginis and Chris Bazinet (St. John’s, New York)
Facilitator Pete Mirabito (University of Kentucky)
Goals: Students will understand
That segregation of chromosomes gives rise to Mendelian
ratios
The relationship between genotype and phenotype
The principle of a test cross
Mendel’s two laws and linkage
That most mutations are recessive
Inheritance in humans (pedigree analysis)
Outcomes: Students will be able to
Distinguish sex-linked from autosomal inheritance
Predict distribution of gamete genotypes given parental genotype
Define the following terms: haploid, diploid, allele, gene,
homologs, dominant, recessive, sex-linked, autosomal, genotype,
phenotype, wild-type, mutants, hemizygous, homozygous,
heterozygous
Determine the relationship between genotype and phenotype
Solve genetic problems: monohybrid cross, dihybrid cross, sexlinked
Solve genetic problems: sum rule, product rule (basic probability)
Teachable Tidbit: Case-Study in Human
Genetics
Recently completed experiments with peas and
flies (Mendel’s two laws)
How can we learn about human genes when we
cannot do controlled crosses?
A Case Study in Human Genetics
Goal: apply principles of Mendelian genetics to human
inheritance
Learning Outcomes:
You will be able to determine the mode of
inheritance from pedigrees.
You will be able to apply rules of probability to
pedigrees.
In the following video, you might observe an important
feature of the disease.
In the video, what observations did you make?
Please brainstorm.
Pedigree Symbols
Carrier female
Royal Family Pedigree
Victoria
Princess of Saxe-Coberg
1786-1861
Edward
Duke of Kent
1767-1820
Victoria
Queen of England
1819-1901
Albert
1819-1861
Edward VII
Of England
Victoria Frederick
Wilhelm
Sophia
of Greece
Alexandra
George V
George
VI
Princess
Margaret
Queen Elizabeth Prince Phillip
Alice
Louis of Hesse Alfred
Irene Henry Fred
Alix
Helena
Louise
Nikolas of Russia
Arthur
Lady May
Abel Smith
Waldemar Prince Henry Olga Tatiana Marie Anastasia Alexie
Sigmund
of Prussia
Leopold
Helen
Beatrice
Henry
Alice of Athelon Alfonso XIII of Spain Eugenic Leopold Maurice
Rupert
Alfonso
(adapted from a case study by Yelena Aronova-Tiuntseva and Clyde Freeman Herreid
University at Buffalo, State University of New York)
Gonzalo
Juan Carlos
What type of inheritance does the
pedigree suggest?
A.
B.
C.
D.
E.
X
X-linked dominant
X-linked recessive
Y-linked
autosomal recessive
autosomal dominant
X
X
Who are the carriers?
XhY
I.
XhXH
XhXH
XhXH
XH Y
II.
XH Y
XH Y
XhY
XhY
XH Y
XH Y
XH Y
XHY
XH Y
XhY
V.
XH Y
Xh Y
III.
IV.
XH Y
X hY
XH Y
XH Y
Royal Family Pedigree with carrier
females revealed
If a hemophilic male marries an unaffected
female (non-carrier), what is the probability
that they have an affected child?
A.
B.
C.
D.
E.
0
0.25
0.50
0.75
1.00
Thus, the correct answer
is 0
If a hemophilic male marries an unaffected female
(non-carrier) and they have a daughter, what is the
probability that she will be a carrier?
A.
B.
C.
D.
E.
0
0.25
0.50
0.75
1.00
Thus, the correct answer
is 1
Summary
1. Hemophilia is an X-linked recessive disorder
2. Hemophilia is typically expressed in males and
carried by females
3. Hemophilia affects all races and ethnic groups
equally
HW Assignment: Construct a pedigree of a different
X-linked disease: SCID by going to homework 3 at
course management site
http://ghr.nlm.nih.gov/condition/x-linked-severecombined-immunodeficiency
Assignment: Construct a pedigree of a
different X-linked disease:
SCID
Draw a pedigree and identify: carriers, affected individuals, informative
individuals , and individuals of unknown genotype. Calculate the probability
that a female of unknown genotype is a carrier.
The mating pair is a carrier woman and an unaffected male.
They have 5 daughters and 3 sons:
Daughter 1 gets married and has 3 girls and one boy who dies in
infancy.
Daughters 2 and 3 get married and have two boys each that go on to
marry and have one boy each that lives to be an adult.
Daughter 4 gets married and has 4 daughters and no sons.
Daughter 5 has three sons and two daughters. One of the sons dies in
infancy.