PowerPoint PresentationCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
From PowerPoint® Lectures for Biology: Concepts & Connections
CHAPTER 9
Purebreds and Mutts — A Difference of Heredity
Genetics is the science of heredity
These black Labrador puppies are purebred—their parents and grandparents were black Labs with very similar genetic makeups
Purebreds
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The parents of these puppies were a mixture of different breeds
Their behavior and appearance is more varied as a result of their diverse genetic inheritance
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9.1 The science of genetics has ancient roots
The science of heredity dates back to ancient attempts at selective breeding
Until the 20th century, however, many biologists erroneously believed that
characteristics acquired during lifetime could be passed on
characteristics of both parents blended irreversibly in their offspring
MENDEL’S PRINCIPLES
9.2 Experimental genetics began in an abbey garden
Modern genetics began with Gregor Mendel’s quantitative experiments with pea plants
Figure 9.2A, B
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Mendel crossed pea plants that differed in certain characteristics and traced the traits from generation to generation
Figure 9.2C
1
White
Stamens
Carpel
Purple
PARENTS
(P)
OFF-SPRING
(F1)
2
Transferred pollen from stamens of white flower to carpel of purple flower
3
4
Mendel studied seven pea characteristics
Figure 9.2D
He hypothesized that there are alternative forms of genes (although he did not use that term), the units that determine heredity
FLOWER
COLOR
FLOWER
POSITION
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9.3 Mendel’s principle of segregation describes the inheritance of a single characteristic
From his experimental data, Mendel deduced that an organism has two genes (alleles) for each inherited characteristic
One characteristic comes from each parent
P GENERATION
Fertilization among F1 plants
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A sperm or egg carries only one allele of each pair
The pairs of alleles separate when gametes form
This process describes Mendel’s law of segregation
Alleles can be dominant or recessive
GENETIC MAKEUP (ALLELES)
Figure 9.3B
9.4 Homologous chromosomes bear the two alleles for each characteristic
Alternative forms of a gene (alleles) reside at the same locus on homologous chromosomes
GENE LOCI
Figure 9.4
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9.5 The principle of independent assortment is revealed by tracking two characteristics at once
By looking at two characteristics at once, Mendel found that the alleles of a pair segregate independently of other allele pairs during gamete formation
This is known as the principle of independent assortment
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Figure 9.5A
Figure 9.5B
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9.6 Geneticists use the testcross to determine unknown genotypes
The offspring of a testcross often reveal the genotype of an individual when it is unknown
TESTCROSS:
B_
GENOTYPES
bb
BB
Bb
or
GAMETES
OFFSPRING
Inheritance follows the rules of probability
The rule of multiplication and the rule of addition can be used to determine the probability of certain events occurring
F1 GENOTYPES
Bb female
F2 GENOTYPES
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9.8 Connection: Genetic traits in humans can be tracked through family pedigrees
The inheritance of many human traits follows Mendel’s principles and the rules of probability
Figure 9.8A
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Family pedigrees are used to determine patterns of inheritance and individual genotypes
Figure 9.8B
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9.9 Connection: Many inherited disorders in humans are controlled by a single gene
Most such disorders are caused by autosomal recessive alleles
Examples:
A few are caused by dominant alleles
Figure 9.9B
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Table 9.9
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9.10 Connection: Fetal testing can spot many inherited disorders early in pregnancy
Karyotyping and biochemical tests of fetal cells and molecules can help people make reproductive decisions
Fetal cells can be obtained through amniocentesis
Figure 9.10A
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Chorionic villus sampling is another procedure that obtains fetal cells for karyotyping
Figure 9.10B
Examination of the fetus with ultrasound is another helpful technique
Figure 9.10C, D