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1. Pedigree Analysis
• The Study of Genetics in Humans Is Constrained
by Special Features of Human Biology and Culture
• Geneticists Often Use Pedigrees to Study the
Inheritance of Characteristics in Humans
• Analysis of Pedigrees Requires Recognizing
Patterns Associated with Different Modes of
Inheritance
• The Study of Twins Can Be Used to Assess the
Importance of Genes and Environment on
Variation in a Trait

2. • Adoption Studies Are Another Technique for
Examining the Effects of Genes and Environment
on Variation in Traits
• Genetic Counseling Provides Information to Those
Concerned about Genetic Diseases and Traits,
• Genetic Testing Provides Information about the
Potential for Inheriting or Developing a Genetic
Condition,
• Comparison of Human and Chimpanzee Genomes
Is Helping to Reveal Genes That Make Humans
Unique,

3. The Study of Genetics in Humans Is
Constrained by Special Features of Human
Biology and Culture
• Special features:
• Controlled mating is not possible
• Long generation time
• Small family size

4. • Pedigree: pictorial representation of a family
history, a family tree that outlines the inheritance
of one or more characteristics
• Proband: the person with whom the pedigree
is initiated
Geneticists Often Use Pedigrees to Study the
Inheritance of Characteristics in Humans

7. • Autosome Recessive Traits
6.3 Analysis of Pedigrees Requires
Recognizing Patterns Associated with Different
Modes of Inheritance

9. •6.4 Autosomal recessive traits normally appear with equal
frequency in both sexes and seem to skip generations.

10. • Autosomal Dominant Traits
6.3 Analysis of Pedigrees Requires
Recognizing Patterns Associated with Different
Modes of Inheritance

12. •6.5 Autosomal dominant traits normally appear with equal
frequency in both sexes and do not skip generations.

13. • X-Linked Recessive Traits
6.3 Analysis of Pedigrees Requires
Recognizing Patterns Associated with Different
Modes of Inheritance

15. •6.7 X-linked recessive traits appear more often in males
than in females and are not passed from father to son

17. •6.8 Classic hemophilia is inherited as an X-linked
recessive trait. This pedigree is of hemophilia in the royal
families of Europe.

18. • X-Linked Dominant Traits
6.3 Analysis of Pedigrees Requires
Recognizing Patterns Associated with Different
Modes of Inheritance

20. •6.9 X-linked dominant traits affect both males and
females. An affected male must have an affected mother.

21. • Y-Linked Traits
6.3 Analysis of Pedigrees Requires
Recognizing Patterns Associated with Different
Modes of Inheritance

23. •6.10 Y-linked traits appear only in males and are passed
from a father to all his sons

24. The Study of Twins Can Be Used to Assess the
Importance of Genes and Environment on Variation
in a Trait
• Dizygotic twins = non-identical twins
• Monozygotic twins = identical twins
• Concordant trait: the trait shared by both
members of a twin pair
• Concordance: the percentage of twin pairs that
are concordant for a trait

26. The Study of Twins Can Be Used to Assess the
Importance of Genes and Environment on Variation
in a Trait
• Twin Studies and Obesity

29. •6.14 Adoption studies demonstrate that obesity has a
genetic influence. [Redrawn with the permission of the
New England Journal of Medicine 314:195, 1986.]

31. •6.14 Adoption studies demonstrate that obesity has a
genetic influence. [Redrawn with the permission of the
New England Journal of Medicine 314:195, 1986.]

32. 6.6 Genetic Counseling Provides Information to
Those Concerned about Genetic Diseases and
Traits
• Genetic counseling: provides information related
to hereditory conditions

36. •6.16 Amniocentesis is a procedure for obtaining fetal cells
for genetic testing.

38. •6.17 Chorionic villus sampling (CVS) is another procedure
for obtaining fetal cells for genetic testing

39. 6.8 Comparison of Human and Chimpanzee
Genomes Is Helping to Reveal Genes That Make
Humans Unique
• Microcephalin 1 to microcephalin 6 regulates
human brain size.
• FOXP 2 regulates human speech.