chapter 9 patterns of inheritance
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CHAPTER 9 Patterns of Inheritance. Modules 9.1 – 9.10. 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 - PowerPoint PPT PresentationTRANSCRIPT
BIOLOGYCONCEPTS & CONNECTIONS
Fourth Edition
Copyright © 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 9Patterns of Inheritance
Modules 9.1 – 9.10
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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 often suffer from serious genetic defects
Purebreds and Mutts — A Difference of Heredity
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canine hip dysplasia
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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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• 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
9.1 The science of genetics has ancient roots
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• The inheritance of acquired characters (or characteristics) is the hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged through use) are purportedly transmitted to offspring. It is also commonly referred to as the theory of adaptation equated with the evolutionary theory of French naturalist Jean-Baptiste Lamarck (1744-1829).
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Genetic Disproof
• There are many formulations of the genetic disproof, but all have roughly the same structure as the following:
• Acquired traits do not affect an organism's genome.
• Only the genome is passed to the offspring.
• Therefore, acquired traits cannot be passed to the offspring.
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• Modern genetics began with Gregor Mendel’s quantitative experiments with pea plants
9.2 Experimental genetics began in an abbey garden
Figure 9.2A, B
Stamen
Carpel
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Mendel crossed pea plants that differed in certain characteristics and traced the traits from generation to generation
Figure 9.2C
• This illustration shows his technique for cross-fertilization
1 Removed stamensfrom purple flower
White
Stamens
Carpel
PurplePARENTS(P)
OFF-SPRING
(F1)
2 Transferred pollen from stamens of white flower to carpel of purple flower
3 Pollinated carpel matured into pod
4 Planted seeds from pod
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• 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
SEED COLOR
SEED SHAPE
POD SHAPE
POD COLOR
STEM LENGTH
Purple White
Axial Terminal
Yellow Green
Round Wrinkled
Inflated Constricted
Green Yellow
Tall Dwarf
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Punnett Squares
• Professor Reginald Crundall Punnett, FRS (June 20, 1875 – January 3, 1967) was a British geneticist who co-founded, with William Bateson, the Journal of Genetics in 1910. Punnett is probably best remembered today as the creator of the Punnett square, a tool still used by biologists to predict the probability of possible genotypes of offspring. His Mendelism (1905) is sometimes said to have been the first textbook on genetics; it was probably the first popular science book to introduce genetics to the public.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• From his experimental data, Mendel deduced that an organism has two genes (alleles) for each inherited characteristic
– One characteristic comes from each parent
9.3 Mendel’s principle of segregation describes the inheritance of a single characteristic
P GENERATION(true-breedingparents)
F1 generation
F2
generation
Purple flowers White flowers
All plants have purple flowers
Fertilization among F1 plants(F1 x F1)
3/4 of plantshave purple flowers
1/4 of plantshave white flowers
Figure 9.3A
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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 1. Law of segregation
– 2. Alleles can be dominant or recessive
GENETIC MAKEUP (ALLELES)
P PLANTS
F1 PLANTS(hybrids)
F2 PLANTS
PP pp
All P All p
All Pp
1/2 P 1/2 p
EggsP
p
P
PPp
Sperm
Pp Pp
pp
Gametes
Gametes
Phenotypic ratio3 purple : 1 white
Genotypic ratio1 PP : 2 Pp : 1 pp
Figure 9.3B
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• Alternative forms of a gene (alleles) reside at the same locus on homologous chromosomes- One allele is dominant over the other with regard to Mendelian Traits.
9.4 Homologous chromosomes bear the two alleles for each characteristic
GENE LOCI
Figure 9.4
P a B
DOMINANTallele
RECESSIVEallele
P a b
GENOTYPE: PP aa Bb
HOMOZYGOUSfor thedominant allele
HOMOZYGOUSfor therecessive allele
HETEROZYGOUS
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• 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:
3. Principle of independent assortment
9.5 The principle of independent assortment is revealed by tracking two characteristics at once
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Figure 9.5A
HYPOTHESIS: DEPENDENT ASSORTMENT
HYPOTHESIS: INDEPENDENT ASSORTMENT
PGENERATION
F1
GENERATION
F2
GENERATION
RRYY rryy
Gametes RY
Yellowround
ry
RrYy
Eggs SpermRY
ry
RY
ry
1/21/2
1/21/2
Actual resultscontradict hypothesis
RRYY rryy
RY ryGametes
RrYy
Eggs RY
rY
1/4
1/4
Ry
ry
1/4
1/4
RY
rY
Ry
ry
1/4
1/4
1/4
1/4
RRYY
RrYYRrYY
RRYy rrYY RrYy
RrYyRrYyRrYyRrYy
rrYy RRyy rrYy
Rryy Rryy
rryy
9/16
3/16
3/16
1/16
Greenround
Yellowwrinkled
Yellowwrinkled
ACTUAL RESULTSSUPPORT
HYPOTHESIS
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• Independent assortment of two genes in the Labrador retriever
Figure 9.5B
PHENOTYPES Black coat, normal vision
B_N_
Blind
GENOTYPES
MATING OF HETEROZYOTES(black, normal vision)
PHENOTYPIC RATIO OF OFFSPRING
Black coat, blind (PRA)
B_nn
Chocolate coat, normal vision
bbN_
Chocolate coat, blind (PRA)
bbnn
9 black coat,normal vision
3 black coat,blind (PRA)
3 chocolate coat,normal vision
1 chocolate coat,blind (PRA)
Blind
BbNnBbNn
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http://www.athro.com/evo/gen/punexam.html
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A dihybrid cross
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The Female Calico Cat-X-Linked Calico coloring is a mix of phaeomelanin based colors (red) and eumelanin based color (black, chocolate and cinnamon). Cats of this coloration are believed to bring good luck in the folklore of many cultures.[1]
The spotting gene causes white patches to cover the colored fur
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4 Sex-Linked Traits:
1. Normal Color Vision: A: 29, B: 45, C: --, D: 26
2. Red-Green Color-Blind: A: 70, B: --, C: 5, D: --
3. Red Color-blind: A: 70, B: --, C: 5, D: 6
4. Green Color-Blind: A: 70, B: --, C: 5, D: 2
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• The offspring of a testcross often reveal the genotype of an individual when it is unknown
9.6 Geneticists use the testcross to determine unknown genotypes
TESTCROSS:
B_GENOTYPES bb
BB Bbor
Two possibilities for the black dog:
GAMETES
OFFSPRING All black 1 black : 1 chocolate
B
b
B
b
b
Bb Bb bb
Figure 9.6
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• Most such disorders are caused by autosomal recessive alleles
– Examples: cystic fibrosis, sickle-cell disease
9.9 Connection: Many inherited disorders in humans are controlled by a single gene
Figure 9.9A
D D
d d
NormalDd
NormalDd
DDNormal
DdNormal(carrier)
DdNormal(carrier)
ddDeaf
Eggs Sperm
PARENTS
OFFSPRING
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• 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
9.7 Mendel’s principles reflect the rules of probability
F1 GENOTYPES
Bb female
F2 GENOTYPES
Formation of eggs
Bb male
Formation of sperm
1/2
1/2
1/2
1/21/4
1/41/4
1/4
B B
B B
B B
b
b b
b
b b
Figure 9.7
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• The inheritance of many human traits follows Mendel’s principles and the rules of probability
9.8 Connection: Genetic traits in humans can be tracked through family pedigrees
Figure 9.8A
OMIM-
http://www.ncbi.nlm.nih.gov/sites/entrez?db=omim
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• Family pedigrees are used to determine patterns of inheritance and individual genotypes
Figure 9.8B
DdJoshuaLambert
DdAbigailLinnell
D_Abigail
Lambert
Female
DdElizabeth
Eddy
D_JohnEddy
? D_HepzibahDaggett
?
?
ddDdDdDdddDdDd
MaleDeaf
Hearing
ddJonathanLambert
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• A few are caused by dominant alleles
Figure 9.9B
– Examples: achondroplasia, Huntington’s disease