Observable Observable Patterns of Patterns of InheritanceInheritance
Can you do this?Can you do this?
Terms to KnowTerms to Know
ProbabilityProbability True-breedingTrue-breeding HybridHybrid SegregationSegregation TraitsTraits GenesGenes
HomozygousHomozygous HeterozygousHeterozygous PhenotypePhenotype GenotypeGenotype DominantDominant RecessiveRecessive
GenesGenes Chemical factors that determine Chemical factors that determine
traits (units of information)traits (units of information) Analogy: Genes are like a Analogy: Genes are like a
combination of ingredients in a combination of ingredients in a recipe. They code for a specific recipe. They code for a specific food.food.
Passed from parents to offspringPassed from parents to offspring Each has a specific location (Each has a specific location (locuslocus) )
on a chromosomeon a chromosome
AllelesAlleles
Different forms of a gene (back to Different forms of a gene (back to analogy…replacing jiffy p.b. with analogy…replacing jiffy p.b. with skippy p.b.) skippy p.b.)
DominantDominant allele (Uppercase allele (Uppercase letter) overrules a letter) overrules a recessiverecessive allele allele (lowercase letter) that it is paired (lowercase letter) that it is paired withwith
Allele CombinationsAllele Combinations
HomozygousHomozygous = =purebredpurebred having two identical alleles at a locushaving two identical alleles at a locus AA (dominant expressed)AA (dominant expressed) or or aa aa
(recessive expressed)(recessive expressed) HeterozygousHeterozygous = =hybridhybrid
having two different alleles at a locushaving two different alleles at a locus Aa (dominant expressed)Aa (dominant expressed)
Genotype & PhenotypeGenotype & Phenotype
Genotype refers to particular genes Genotype refers to particular genes an individual carriesan individual carries
Phenotype refers to an individual’s Phenotype refers to an individual’s observable traitsobservable traits
Cannot always determine genotype Cannot always determine genotype by observing phenotypeby observing phenotype
Tracking GenerationsTracking Generations
Parental generation Parental generation PPmates to produce mates to produce
First-generation offspring First-generation offspring FF11
mate to produce mate to produce
Second-generation offspring Second-generation offspring FF22
Earlobe Variation Earlobe Variation
Whether a person is born with Whether a person is born with attached or detached earlobes attached or detached earlobes depends on a single genedepends on a single gene
Gene has two molecular forms Gene has two molecular forms (alleles)(alleles)
Earlobe VariationEarlobe Variation
You inherited one allele for this gene You inherited one allele for this gene from each parentfrom each parent
Dominant allele specifies detached Dominant allele specifies detached earlobes (E)earlobes (E)
Recessive allele specifies attached Recessive allele specifies attached earlobes (e)earlobes (e)
Dominant & Recessive Dominant & Recessive AllelesAlleles
If you have attached earlobes, you If you have attached earlobes, you inherited two copies of the recessive inherited two copies of the recessive alleleallele
If you have detached earlobes, you If you have detached earlobes, you may have either one or two copies of may have either one or two copies of the dominant allelethe dominant allele
Early Ideas About Early Ideas About Heredity Heredity
People knew that sperm and People knew that sperm and eggs transmitted information eggs transmitted information about traitsabout traits
Blending theoryBlending theory Problem:Problem:
Would expect variation to Would expect variation to disappeardisappear
Variation in traits persistsVariation in traits persists
Gregor MendelGregor Mendel
Strong background Strong background in plant breeding in plant breeding and mathematicsand mathematics
Using pea plants, Using pea plants, found indirect but found indirect but observable evidence observable evidence of how parents of how parents transmit genes to transmit genes to offspringoffspring
Mendel was born in1822Mendel was born in1822 Austrian monkAustrian monk Studied at the Univ. of ViennaStudied at the Univ. of Vienna Teacher (High School)Teacher (High School)
FilamentAnther
StigmaStyle
Ovary
Carpel
PetalSepal
Ovule
Stamen
Section 24-1Figure 24–5 The Structure of a Flower
The Garden Pea PlantThe Garden Pea Plant
Self-pollinatingSelf-pollinating True breeding (different True breeding (different
alleles not normally alleles not normally introduced)introduced)
Can be experimentally cross-Can be experimentally cross-pollinatedpollinated
How did Mendel fertilize the
plants?
FF11 Results of One Results of One Monohybrid CrossMonohybrid Cross
F M
Dominant trait is
expressed
Recessive appears
Seed Shape
Flower Position
Seed CoatColor
Seed Color
Pod Color
Plant Height
PodShape
Round
Wrinkled
Round
Yellow
Green
Gray
White
Smooth
Constricted
Green
Yellow
Axial
Terminal
Tall
Short
Yellow Gray Smooth Green Axial Tall
Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants
FF11 Results of Mendel’s Results of Mendel’s Dihybrid CrossesDihybrid Crosses
All plants displayed the dominant All plants displayed the dominant
form of both traits form of both traits
We now know:We now know:
All plants inherited one allele for each All plants inherited one allele for each
trait from each parenttrait from each parent
All plants were heterozygous (All plants were heterozygous (AaBbAaBb))
Principle of DominancePrinciple of Dominance
Some alleles are dominant and Some alleles are dominant and others are recessive.others are recessive.
Mendel wanted to know if the Mendel wanted to know if the recessive alleles disappeared or are recessive alleles disappeared or are they still in the f1,just hidden.they still in the f1,just hidden.
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Principles of Dominance
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Principles of Dominance
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Principles of Dominance
Mendel’s Theory Mendel’s Theory of Segregationof Segregation
An individual inherits a unit of An individual inherits a unit of information (allele) about a trait information (allele) about a trait from each parentfrom each parent
During gamete formation, the alleles During gamete formation, the alleles segregate from each other segregate from each other
Independent AssortmentIndependent Assortment
Mendel concluded that the two Mendel concluded that the two “units” for the first trait were to be “units” for the first trait were to be assorted into gametes independently assorted into gametes independently of the two “units” for the other traitof the two “units” for the other trait
Members of each pair of homologous Members of each pair of homologous chromosomes are sorted into chromosomes are sorted into gametes at random during meiosis gametes at random during meiosis
Independent AssortmentIndependent Assortment
Metaphase I
Metaphase II:
Gametes:
1/4 AB 1/4 ab 1/4 Ab 1/4 aB
A A A A
A A A A
AAAA
B B
B B
BB
B B
BBBB
a a a a
aa aa
aaaa
bb b b
bb b b
b b b b
OR
FF22 Results of Results of Monohybrid CrossMonohybrid Cross
Type of alleles
The physical characteristic
Impact of Mendel’s WorkImpact of Mendel’s Work
Mendel presented his results in Mendel presented his results in 18651865
Paper received little noticePaper received little notice Mendel discontinued his Mendel discontinued his
experiments in 1871experiments in 1871 Paper rediscovered in 1900 and Paper rediscovered in 1900 and
finally appreciated finally appreciated
ProbabilityProbability
The likelihood that a particular event The likelihood that a particular event will occur.will occur.
Flip a coin.Flip a coin. We use Punnett SquaresWe use Punnett Squares
D 38- Deduce the probable mode of D 38- Deduce the probable mode of inheritance of traits (e.g., inheritance of traits (e.g.,
Punnett Squares of Test Crosses
Homozygous recessive
a a
A
a aa
Aa Aa
aa
Homozygous recessive
a a
A
A Aa
Aa Aa
Aa
Two phenotypes All dominant phenotype
Punnett Square of a Punnett Square of a Monohybrid CrossMonohybrid Cross
Female gametes
Male gametes
A a
A
a Aa
AA Aa
aa
Dominant phenotype canarise 3 ways,recessive only one
Test CrossTest Cross
Individual that shows dominant Individual that shows dominant phenotype is crossed with individual phenotype is crossed with individual with recessive phenotypewith recessive phenotype
Examining offspring allows you to Examining offspring allows you to determine the genotype of the determine the genotype of the dominant individualdominant individual
Tt X Tt Cross
Tt X Tt Cross
Tt X Tt Cross
Genetics Practice Genetics Practice Problem 1Problem 1
What occurs when a purple plant What occurs when a purple plant that is heterozygous is fertilized by a that is heterozygous is fertilized by a white plant?white plant?
Identify generationsIdentify generations Punnett SquarePunnett Square Genotypes %Genotypes % Phenotype %Phenotype %
Principle of Independent Principle of Independent AssortmentAssortment
The genes for different traits The genes for different traits separate independently of one separate independently of one another during the formation of another during the formation of gametes.gametes.
Figure 11-10 Independent Assortment in Peas
Yellow round 9/16Yellow round 9/16 Green round 3/16Green round 3/16 Yellow wrinkled 3/16Yellow wrinkled 3/16 Green wrinkled 1/16Green wrinkled 1/16
9 : 3 : 3 : 1 Ratio9 : 3 : 3 : 1 Ratio
Dihybrid Cross Dihybrid Cross
Experimental cross between Experimental cross between individuals that are homozygous individuals that are homozygous
for different versions of for different versions of twotwo traits traits
Straight Thumb (Dominant)
Curved Thumb (Recessive)
Straight Pinky (Dominant)
Bent Pinky (Recessive)
More Dominant Traits
Polydactylism Achondroplastic Dwarfism
Tay-Sachs Disease - One Wrong Letter
Dominance Relations Dominance Relations
Complete dominance Complete dominance Incomplete dominanceIncomplete dominance
Heterozygote phenotype is somewhere Heterozygote phenotype is somewhere between that of two homozyotesbetween that of two homozyotes
CodominanceCodominance Non-identical alleles specify two Non-identical alleles specify two
phenotypes that are both expressed in phenotypes that are both expressed in heterozygotesheterozygotes
Flower Color in Flower Color in Snapdragons: Snapdragons:
Incomplete DominanceIncomplete Dominance
Red-flowered plant X White-flowered Red-flowered plant X White-flowered
plantplant
Pink-flowered Pink-flowered FF11 plants plants
(homozygote) (homozygote)
(heterozygotes)
Flower Color in Flower Color in Snapdragons: Incomplete Snapdragons: Incomplete
DominanceDominance Red flowers - two alleles allow them Red flowers - two alleles allow them
to make a red pigmentto make a red pigment White flowers - two mutant alleles; White flowers - two mutant alleles;
can’t make red pigmentcan’t make red pigment Pink flowers have one normal and Pink flowers have one normal and
one mutant allele; make a smaller one mutant allele; make a smaller amount of red pigmentamount of red pigment
Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
Flower Color in Flower Color in Snapdragons: Incomplete Snapdragons: Incomplete
DominanceDominance
Pink-flowered plant X Pink-flowered Pink-flowered plant X Pink-flowered
plantplant
White-, pink-, and red-flowered plants White-, pink-, and red-flowered plants in a 1:2:1 ratioin a 1:2:1 ratio
(heterozygote) (heterozygote)
Incomplete DominanceIncomplete Dominance
Neither allele is dominant
over the other
Combination of red and
white flowers
CodominantCodominant
Sickle Cell DiseaseSickle Cell Disease ABO Blood TypesABO Blood Types
Pleitropy Pleitropy
Alleles at a single locus may have Alleles at a single locus may have effects on two or more traitseffects on two or more traits
Classic example is the effects of the Classic example is the effects of the mutant allele at the beta-globin mutant allele at the beta-globin locus that gives rise to sickle-cell locus that gives rise to sickle-cell anemiaanemia
Teachers Domain - A Mutation Story
Genetics of Sickle-Cell Genetics of Sickle-Cell AnemiaAnemia
Two allelesTwo alleles1) 1) HbHbAA
Encodes normal beta hemoglobin Encodes normal beta hemoglobin chainchain
2) 2) HbHbSS
Mutant allele encodes defective Mutant allele encodes defective chainchain
HbHbSS homozygotes produce only the homozygotes produce only the defective hemoglobin; suffer from defective hemoglobin; suffer from sickle-cell anemiasickle-cell anemia
Pleiotrophic Effects of Pleiotrophic Effects of HbHbSS/Hb/HbSS
At low oxygen levels, cells with only At low oxygen levels, cells with only HbHbSS hemoglobin “sickle” and stick hemoglobin “sickle” and stick togethertogether
This impedes oxygen delivery and This impedes oxygen delivery and blood flowblood flow
Over time, it causes damage Over time, it causes damage throughout the bodythroughout the body
Blood TypingBlood Typing
Karl Landsteiner 1897Karl Landsteiner 1897 Worked at the Univ. of Vienna, Worked at the Univ. of Vienna,
Vienna Austria (Sound familiar?)Vienna Austria (Sound familiar?) Wanted to find out which red blood Wanted to find out which red blood
cells would clotcells would clot
First found two different groups, A First found two different groups, A and Band B
Third group would not clot when Third group would not clot when exposed to A or B What do you think exposed to A or B What do you think this was?this was?
What about the forth group?What about the forth group?
Genetics of ABO Blood Genetics of ABO Blood Types: Three AllelesTypes: Three Alleles
Gene that controls ABO type codes Gene that controls ABO type codes for enzyme that dictates structure of for enzyme that dictates structure of a glycolipid on blood cellsa glycolipid on blood cells
Two alleles (Two alleles (IIAA and and IIBB) are ) are codominant when pairedcodominant when paired
Third allele (Third allele (ii) is recessive to others) is recessive to others
ABO Blood Type:ABO Blood Type: Glycolipids on Red Cells Glycolipids on Red Cells
Type A - Glycolipid A on cell surfaceType A - Glycolipid A on cell surface
Type B - Glycolipid B on cell surfaceType B - Glycolipid B on cell surface
Type AB - Both glyocolipids A & BType AB - Both glyocolipids A & B
Type O - Neither glyocolipid A nor BType O - Neither glyocolipid A nor B
ABO Blood Type:ABO Blood Type:Allele CombinationsAllele Combinations
Type A - Type A - IIAAIIAA or or IIAAii
Type B - Type B - IIBBIIBB oror I IBBii
Type AB - Type AB - IIAAIIBB
Type O - Type O - iiii
ABO and TransfusionsABO and Transfusions
Recipient’s immune system will Recipient’s immune system will
attack blood cells that have an attack blood cells that have an
unfamiliar glycolipid on surfaceunfamiliar glycolipid on surface
Type O is universal donor because it Type O is universal donor because it
has neither type A nor type B has neither type A nor type B
glycolipidglycolipid
Codominance and Codominance and Multiple Alleles - AB or Multiple Alleles - AB or
NOT AB NOT AB
Codominance - both alleles are dominant
IA and IB
Multiple Alleles - genes have more than two alleles
IA, IB, Ia
Phenotype(Blood Type Genotype
Antigen on Red Blood Cell
Safe Transfusions
To From
Figure 14-4 Blood Groups
Universal Acceptor
Universal Donor
Rh factor - Another Rh factor - Another Blood TraitBlood Trait
Pregnancy complications Pregnancy complications Rh is a type of protein in the bloodRh is a type of protein in the blood If an Rh- man reproduces with an Rh If an Rh- man reproduces with an Rh
+ woman complications can occur.+ woman complications can occur.
Polygenic Traits: Polygenic Traits: Desiree’s Baby Case Desiree’s Baby Case
StudyStudy More than one gene controls a traitMore than one gene controls a trait Skin color more than one gene, Skin color more than one gene,
incomplete dominanceincomplete dominance
A,B and C are dark a,b and c are light
Sex Linked Traits - Sex Linked Traits - traits that are carried traits that are carried on the either the x or y on the either the x or y
chromosomechromosome
Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Male
Female
Figure 14-13 Colorblindness
Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Male
Female
Figure 14-13 Colorblindness
ColorblindnessColorblindness
Cystic Fibrosis - Finding Cures is Hard
Sex-Linked DisorderSex-Linked Disorder
Male Pattern Baldness (X chromosome)
Hairy Pinna - long hair on ears
Chromosome # 7
CFTR gene
The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein.
Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane.
The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus.
Figure 14-8 The Cause of Cystic Fibrosis
Recessive DisorderRecessive Disorder
AlbinismAlbinism
Phenotype results when pathway for Phenotype results when pathway for melanin production is completely melanin production is completely blockedblocked
Genotype - Homozygous recessive at Genotype - Homozygous recessive at the gene locus that codes for the gene locus that codes for tyrosinase, an enzyme in the tyrosinase, an enzyme in the melanin-synthesizing pathwaymelanin-synthesizing pathway
Human Genetics
Tracing Genes Through Tracing Genes Through Families - Human Families - Human
PedigreesPedigrees
Female
Male
Partner
Brothers and Sisters
A circle represents a female.
A square represents a male.
A horizontal line connecting a male and female represents a marriage.
A vertical line and a bracket connect the parents to their children.
A half-shaded circle or square indicates that a person is a carrier of the trait.
A completely shaded circle or square indicates that a person expresses the trait.
A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.
Figure 14-3 A Pedigree
Ability to roll the tongue in the Senator
Family
Tongue Roller - dominant, Non-Tongue Roller - recessive
White = tongue roller, Purple = non-roller
What are the genotypes of everyone? R = roller, r = non roller
George, Sam, Ann, Michael, Daniel and Alan are Rr
Arlene, Tom, Wilma, and Carla are rr
Sandra, Tina and Christopher are either RR or Rr
Case Study - Hemophilia Case Study - Hemophilia and the Royal Familyand the Royal Family
1. First, let’s take a look at Queen Victoria’s son Leopold’s family. His daughter, Alice of Athlone, had one hemophilic son (Rupert) and two other children—a boy and a girl—whose status is unknown. a) What is the probability that her other son was hemophilic? b) What is the probability that her daughter was a carrier? Hemophilic? c) What is the probability that both children were normal?
2. Now for the Spanish connection: Victoria’s youngest child, Beatrice, gave birth to one daughter, one normal son, and two hemophilic sons. Looking at the pedigree of the royal family, identify which of Beatrice’s children received the hemophilic gene; why can you make this conclusion? Notice that Beatrice’s daughter, Eugenie, married King Alfonso XIII of Spain and had six children, one of whom was the father of Juan Carlos, the current King of Spain. Would you predict that Juan Carlos was normal, a carrier, or a hemophilic?
3. Alexis did not die from hemophilia. At the age of fourteen he was executed with the rest of the family. His four oldest sisters were also young and didn’t have children, so we don’t know whether any of them was a carrier. But we can make an estimate. a) What are the probabilities that all four of the girls were carriers of the allele hemophilia? b) Supposing Alexis had lived and married a normal woman, what are the chances that his daughter would be a hemophiliac? c) What are the chances his daughters would be carriers? d) What are the chances that his sons would be hemophiliacs?
Homologous chromosomes fail to separate
Meiosis I:Nondisjunction
Meiosis II
Nondisjunction
Homologous chromosomes fail to separate
Meiosis I:Nondisjunction
Meiosis II
Nondisjunction
Homologous chromosomes fail to separate
Meiosis I:Nondisjunction
Meiosis II
Nondisjunction
Epistasis Epistasis
Interaction between the products of Interaction between the products of gene pairsgene pairs
Common among genes for hair color Common among genes for hair color in mammalsin mammals
Genetics of Coat Color Genetics of Coat Color in Labrador Retrieversin Labrador Retrievers
Two genes involvedTwo genes involved- One gene influences melanin - One gene influences melanin
productionproduction Two alleles -Two alleles - B B (black) is dominant over(black) is dominant over b b
(brown)(brown)
- Other gene influences melanin - Other gene influences melanin depositiondeposition Two alleles -Two alleles - E E promotes pigment promotes pigment
deposition and is dominant overdeposition and is dominant over e e
Allele Combinations Allele Combinations and Coat Color and Coat Color
Black coat - Must have at least one Black coat - Must have at least one
dominant allele at dominant allele at bothboth loci loci
BBEE, BbEe, BBEe,BBEE, BbEe, BBEe, or or BbEE BbEE
Brown coat - Brown coat - bbEE, bbEebbEE, bbEe
Yellow coat - Yellow coat - Bbee, BbEE, bbeeBbee, BbEE, bbee
Comb Shape in PoultryComb Shape in Poultry
Alleles at two loci (Alleles at two loci (RR and and PP) interact ) interact
Walnut comb - Walnut comb - RRPP, RRPp, RrPP, RrPpRRPP, RRPp, RrPP, RrPp Rose comb - Rose comb - RRpp, RrppRRpp, Rrpp Pea comb - Pea comb - rrPP, rrPprrPP, rrPp Single comb - Single comb - rrpprrpp
Campodactyly: Campodactyly: Unexpected Phenotypes Unexpected Phenotypes
Effect of allele varies:Effect of allele varies:
Bent fingers on both handsBent fingers on both hands
Bent fingers on one handBent fingers on one hand
No effectNo effect
Many factors affect gene expressionMany factors affect gene expression
Continuous VariationContinuous Variation
A more or less continuous range of A more or less continuous range of small differences in a given trait small differences in a given trait among individualsamong individuals
The greater the number of genes The greater the number of genes
and environmental factors that affect and environmental factors that affect
a trait, the more continuous the a trait, the more continuous the
variation in versions of that traitvariation in versions of that trait
Human VariationHuman Variation
Some human traits occur as a few Some human traits occur as a few discrete typesdiscrete types Attached or detached earlobes Attached or detached earlobes Many genetic disordersMany genetic disorders
Other traits show continuous Other traits show continuous variationvariation HeightHeight WeightWeight Eye colorEye color
Temperature Effects Temperature Effects on Phenotype on Phenotype
Himalayan rabbits are Himalayan rabbits are Homozygous for an Homozygous for an allele that specifies a allele that specifies a heat-sensitive version of heat-sensitive version of an enzyme in melanin-an enzyme in melanin-producing pathwayproducing pathway
Melanin is produced in Melanin is produced in cooler areas of bodycooler areas of body
Environmental Effects Environmental Effects on Plant Phenotypeon Plant Phenotype
Hydrangea macrophyllaHydrangea macrophylla
Action of gene responsible for floral Action of gene responsible for floral color is influenced by soil aciditycolor is influenced by soil acidity
Flower color ranges from pink to Flower color ranges from pink to blueblue