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Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 10
The Basic Principles
of Heredity
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Terminology
•Phenotype
•Genotype
•Locus
•Allele
•Dominant allele
•Recessive allele
•Homozygous
•Heterozygous
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Mendel’s principles of inheritance
• Segregation
–During meiosis, alleles for each locus
segregate
• Independent assortment
–Alleles of different loci distributed randomly
into the gamete
–Results in recombination
–Production of new gene combinations not
found in parent
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Seven characters in Mendel’s study of pea plants
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
One
of Mendel’s
pea crosses
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Gene
loci
and their
alleles
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Monohybrid cross
• Cross between homozygous parents
• Differ at one locus
• Dihybrid cross
• Differ at two loci
• Test cross
• Between individual of unknown
genotype and homozygous recessive
individual
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Monohybrid
cross in
guinea pigs
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Dihybrid
cross
in
guinea pigs
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Test cross in
guinea pigs
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Genetic ratios can be expressed
as probabilities
• Product rule predicts combined
probability of independent events
• Sum rule predicts combined probability
of mutually exclusive events
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Rules
of probability
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Segregation
• Results from homologous chromosomes
separating during meiosis
• Independent assortment
• Orientation of homologous chromosomes
on the metaphase plate determines how
chromosomes are distributed
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Chromosomal
basis for
segregation
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Linkage
• Tendency for a group of genes on same
chromosome to be inherited together
• Recombination of linked genes
• Results from crossing-over in meiotic
prophase I
• By measuring frequency of
recombination, can construct linkage
map of chromosome
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Two-point
test cross to
detect linkage
in fruit flies
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Crossing-over
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Sex chromosomes
• Cells of females of many species contain
two X chromosomes
• Males have single X chromosome and
single, smaller Y chromosome
• Y chromosome determines male sex in
most species of mammals
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Sex
determination
in mammals
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
X-linked red-green colorblindness
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Dosage compensation in female mammals
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Incomplete dominance
• Heterozygote is intermediate in
phenotype
• Codominance
• Heterozygote simultaneously expresses
the phenotypes of both homozygotes
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Incomplete
dominance
in four o’clocks
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Multiple alleles in rabbits
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Gene
interaction
in chickens
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Epistasis in Labrador retrievers
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
• Norm of reaction
• Range of phenotypic possibilities from a
single genotype under different
environmental conditions
• Example is height in human
–Can be modified by factors such as diet
–Genes that affect height set norm of reaction
–Environment molds phenotype within norm
of reaction
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Biology, Seventh Edition
CHAPTER 10 The Basic Principles of Heredity
Polygenic
inheritance in
human skin
pigmentation
Copyright © 2005 Brooks/Cole — Thomson Learning