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Pedigrees & Human Diseases
Additional Topics in Genetics
Bio 391
PEDIGREES  another way to study
How to read a pedigree…
Carrier female
Carrier male
• What do you think
the F1 generation
(line II) # 2 and #5
offspring represent?
• Can you draw the
Punnett Square for
the Parent
generation? (I)
• Helpful because human breeding experiments
are difficult
• Show how traits are passed down through many
• Based mostly on phenotypes; after the fact
• Show the actual offspring
– Punnett squares show the possible offspring
• Really only works well for single traits
– Not polygenic traits
• Only works for inherited traits
– Environmental factors play a large role in who we are
Inheriting Diseases
• Just like physical traits, some diseases
can be inherited on our chromosomes.
• And, just like physical traits, some are Xlinked, some are recessive, some are
dominant or codominant.
• Are you predisposed??
Human Genetic Disorders
• When a genetic disorder is autosomal
dominant, an individual with AA or Aa has the
– Autosomal dominant disorders are rarely lethal
– When a genetic disorder is autosomal recessive,
only aa individuals have the disorder.
– Recall carriers are usually healthy
Prenatal Testing:
Most children with recessive disorders are born to
parents with a normal phenotype (carriers).
A key to assessing risk –identify carrier status
Recently developed tests for several disorders can
distinguish between normal phenotypes in
heterozygotes from homozygous dominants.
The results allow individuals with a family history of
a genetic disorder to make informed decisions
about having children.
However, issues of confidentiality, discrimination,
and adequate information and counseling arise.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
In utero testing to determine if a child will have a
• Amniocentesis – sample of fluid
surrounding fetus, contains some fetal cells
Fig. 14.17a
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Chorionic villus sampling (CVS)
– Pieces of tissue (chorion connecting mother
and fetus) are removed
Fig. 14.17b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Ethical Dilemma
• You are an employer and have 2 equally
qualified candidates for a job. According
to human resources, one of the candidates
will develop Huntington disease and will
likely be unable to work for longer than 10
years. What do you do?
• GINA – Genetic Information
Nondiscrimination Act of 2008
Genetic Disorders
Gaucher disease
Duschene Muscular
Marfan syndrome
Color blindness
Hurler syndrome
Lesch-Nyhan disease
Edwards Syndrome
Bloom’s syndrome
Prader-Willi Syndrome
Wilson’s disease
Fragile X syndrome
Cystic Fibrosis
Sickle cell anemia
Lou Gehrig’s disease
Cri du Chat syndrome
Huntington Disease
Turner’s syndrome
Klinefelter syndrome
Down syndrome
Fanconi anemia