Pierce Genetics: A Conceptual Approach 3e

Benjamin A. Pierce GENETICS A Conceptual Approach FIFTH EDITION

CHAPTER 6 Pedigree Analysis, Applications, and Genetic Testing

2014 W. H. Freeman and Company 6.1 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

6.2 Geneticists Often Use Pedigrees to Study the Inheritance of Characteristics in Humans Pedigree: pictorial representation of a family history, a family tree that outlines the inheritance of one or more

characteristics. Proband: the person from whom the pedigree is initiated. 6.2 Geneticists Often Use Pedigrees to Study the Inheritance of Characteristics in Humans

Autosomal recessive traits: Fig. 6.4 Autosomal dominant traits: Fig. 6.5 X-linked recessive traits: Fig. 6.7 & 6.8 X-linked dominant traits: Fig. 6.9

Y-inked traits: Fig. 6.10 Concept Check 1 Autosomal recessive traits often appear in pedigrees in which there have been

consanguine mating, because these traits: a. tend to skip generations. b. appear only when both parents carry a copy of the gene for the trait, which is more likely when the parents are related.

c. usually arise in children born to parents who are unaffected. d. appear equally in males and females. Concept Check 1

Autosomal recessive traits often appear in pedigrees in which there have been consanguine mating, because these traits: a. tend to skip generations. b. appear only when both parents carry a copy of the

gene for the trait, which is more likely when the parents are related. c. usually arise in children born to parents who are unaffected. d. appear equally in males and females.

Concept Check 2 How could you distinguish between an autosomal recessive trait with higher penetrance in males and an X-linked

recessive trait? Concept Check 2 How could you distinguish between an autosomal recessive trait with higher

penetrance in males and an X-linked recessive trait? X-linked recessive traits are only passed to sons from mothers, not from fathers.

6.3 Studying Twins and Adoptions Can Help Assess the Importance of Genes and Environment Dizygotic twins = nonidentical 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. Table 6.2

Twin studies and obesity: Table 6.3 Concept Check 3 A trait exhibits 100% concordance in both

monozygotic and dizygotic twins. What conclusion can you draw about the role of genetic factors in determining differences in the trait? a. Genetic factors are extremely important.

b. Genetic factors are somewhat important. c. Genetic factors are unimportant. d. Both genetic and environment factors are important. Concept Check 3

A trait exhibits 100% concordance in both monozygotic and dizygotic twins. What conclusion can you draw about the role of genetic factors in determining differences in the trait?

a. Genetic factors are extremely important. b. Genetic factors are somewhat important. c. Genetic factors are unimportant. d. Both genetic and environment factors are important.

6.4 Genetic Counseling and Genetic Testing Provide Information to Those Concerned About Genetic Diseases and Traits Genetic counseling: provides information

related to hereditary conditions. Interpreting Genetic Testing More than a thousand genetic tests

available Complicated by several factors: Some diseases caused by numerous mutations Incomplete penetrance and environmental

factors Genetic Discrimination and Privacy Many new genetics tests

1970s: African Americans carrying sicklecell trait had difficulty finding employment and health insurance Genetic Information Nondiscrimination Act

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