CHAPTER
10 Heredity
IN THIS CHAPTER
Summary:This chapter examines Mendel’s fundamental laws (law of segrega-
tion, law of independent assortment, and law of dominance) as well as some
classic exceptions to these laws (intermediate inheritance, multiple alleles,
polygenic traits, epistasis, and pleiotropy.) This chapter also covers linkage
(sex linkage, gene linkage, and linkage maps), and chromosomal errors such
as nondisjunction, deletions, duplications, translocations, and inversion.Key Ideas
✪Law of segregation: the two alleles for a trait separate during the
formation of gametes—one to each gamete.
✪Law of independent assortment: inheritance of one trait does not interfere
with the inheritance of another trait.
✪Law of dominance: if two opposite pure-breeding varieties are crossed
(BB×bb), all offspring resemble the BB parent.
✪Linked genes that lie along the same chromosome do not follow the law
of independent assortment.
✪Autosomal recessive disorders: Tay-Sachs, cystic fibrosis, sickle cell
anemia, phenylketonuria.
✪Autosomal dominant disorders: Huntington, achondroplasia.
✪Nondisjunction errors: Down, Klinefelter, Turner syndromes.Introduction
How many times have you heard someone say as they look at a baby, “Awwww, he looks
like his daddy” or “She has her mother’s eyes”? What exactly is it that causes an infant to
look like his or her parents? This question is the basis of the study of heredity—the study98 ❯
KEY IDEA