Human Genetics Lab Human Genetics Lab When Students Are the When Students Are the Subjects…… Subjects……
Human Genetics Lab Human Genetics Lab
When Students Are the Subjects…… When Students Are the Subjects……
Loci, Genes and AllelesLoci, Genes and Alleles
• Locus = area on chromosome Locus = area on chromosome where gene is located where gene is located (plural = loci)(plural = loci)
• Gene = sequence of DNA that Gene = sequence of DNA that codes for a protein, gives rise to codes for a protein, gives rise to physical traitphysical trait
• Alleles = alternative forms of a Alleles = alternative forms of a genegene– Dominant allele masks other allelesDominant allele masks other alleles– Recessive allele is masked Recessive allele is masked
Locus 1Locus 1Locus 2Locus 2
Locus 3Locus 3
Genotype and PhenotypeGenotype and PhenotypeTermTerm DefinitionDefinition ExampleExample
GenotypeGenotype Alleles carried by an individualAlleles carried by an individualAll diploid individuals have two All diploid individuals have two copies of each allele copies of each allelehomozygous = both alleles arehomozygous = both alleles are the same the sameheterozygous = two different heterozygous = two different alleles alleles
EE, Ee, eeEE, Ee, ee
PhenotypePhenotype Physical characteristic or Physical characteristic or appearance of an individualappearance of an individual
free or free or attached attached earlobeearlobe
Earlobe AttachmentEarlobe Attachment
GenotypeGenotype PhenotypePhenotype PhenotypePhenotype
EE or EeEE or Ee
E is dominant E is dominant
over eover e
Free Free earlobeearlobe
eeee Attached Attached EarlobeEarlobe
Solving Genetics ProblemsSolving Genetics Problems
1.1. Convert parental phenotypes to Convert parental phenotypes to genotypesgenotypes
--may need to use info about grandparents or --may need to use info about grandparents or children already born to complete these children already born to complete these genotypesgenotypes
2.2. Use Punnett Square to determine Use Punnett Square to determine genotypes of offspringgenotypes of offspring
3.3. Convert offspring genotypes to Convert offspring genotypes to phenotypesphenotypes
Genetics Problem 6, p. 104Genetics Problem 6, p. 104
George has attached ear lobes. Laura has free George has attached ear lobes. Laura has free earlobes, but she is heterozygous for this trait. earlobes, but she is heterozygous for this trait. What are the chances of their child having free What are the chances of their child having free earlobes?earlobes?
Genotype for Genotype for GeorgeGeorge
Genotype for Genotype for LauraLaura
eeee EeEe
e e e e
Homozygous parents can only pass Homozygous parents can only pass one form of an allele to their offspring. one form of an allele to their offspring.
E e E e
Heterozygous parents can pass either of Heterozygous parents can pass either of two forms of an allele to their offspring. two forms of an allele to their offspring.
Genetics Problem 6, p. 104Genetics Problem 6, p. 104
George has attached ear lobes. Laura has free George has attached ear lobes. Laura has free earlobes, but she is heterozygous for this trait. earlobes, but she is heterozygous for this trait. What are the chances of their child having free What are the chances of their child having free earlobes?earlobes?
Genotype for GeorgeGenotype for George Genotype for LauraGenotype for Laura
eeee EeEe
ee
ee
E e E e
EeEe
EeEe
eeee
eeee
50% free earlobes50% free earlobes50% attached earlobes50% attached earlobes
Genetics Problem 16, p. 105Genetics Problem 16, p. 105Both Willy and Ethyl are heterozygous for earlobe Both Willy and Ethyl are heterozygous for earlobe attachment and also for hitchhiker’s thumb. What are attachment and also for hitchhiker’s thumb. What are the chances of a child with…the chances of a child with……attached earlobes and a hitchhiker’s thumb?…attached earlobes and a hitchhiker’s thumb?…free earlobes and no hitchhiker’s thumb?…free earlobes and no hitchhiker’s thumb?
Genotype for Genotype for WillyWilly
Genotype for Genotype for EthylEthyl
EeHhEeHh EeHhEeHh
EH Eh eH eh EH Eh eH eh EH Eh eH eh EH Eh eH eh
EH Eh eH ehEH Eh eH eh
EH EH
EhEh
eH eH
eheh
EEHHEEHH EEHhEEHh EeHHEeHH EeHhEeHh
EEHhEEHh EEhhEEhh EeHhEeHh EehhEehh
EeHHEeHH EeHhEeHh eeHHeeHH eeHheeHh
EeHhEeHh EehhEehh eeHheeHh eehheehh
……attached earlobes and a hitchhiker’s thumb?attached earlobes and a hitchhiker’s thumb?
……free earlobes and no hitchhiker’s thumb?free earlobes and no hitchhiker’s thumb? E_H_ = 9/16E_H_ = 9/16
eehh = 1/16eehh = 1/16
Lab TodayLab Today
• Simple Inheritance (12 traits)Simple Inheritance (12 traits)• The “Which Classmate Shares the Most The “Which Classmate Shares the Most
Traits with You?” Game: Four student Traits with You?” Game: Four student volunteers – single eliminationvolunteers – single elimination
• ““Direct Comparisons with Individuals” – four Direct Comparisons with Individuals” – four classmates and find % of traits sharedclassmates and find % of traits shared
• Complex Inheritance: Height, ABO blood Complex Inheritance: Height, ABO blood typetype
• Solving Genetics Problems with Punnett Solving Genetics Problems with Punnett squaressquares
Simple InheritanceSimple Inheritance
TraitTrait Your Your PhenotypePhenotype
Your GenotypeYour Genotype
Bent little fingerBent little finger
Not bentNot bent
oror
BB or BbBB or Bb(list any ONE (list any ONE genotype that fits)genotype that fits)
bbbb
Determine your phenotype and potential genotype for each trait.Determine your phenotype and potential genotype for each trait.At a specified time, your instructor will conduct a class tally At a specified time, your instructor will conduct a class tally for all traits. for all traits.
Direct Comparisons with IndividualsDirect Comparisons with Individuals
Your PhenotypeYour Phenotype 11stst personperson
22ndnd personperson
attached earlobeattached earlobe 20%20% ----
widow’s peakwidow’s peak ---- 20%20%
hitchhiker’s thumbhitchhiker’s thumb 20%20% ----
pigmented irispigmented iris 20%20% ----
long index fingerlong index finger ---- 20%20%
% Traits Shared% Traits Shared 60%60% 40%40%
Sex-Influenced Traits Change Sex-Influenced Traits Change Dominance Pattern by GenderDominance Pattern by Gender
TraitTrait MalesMales FemalesFemales
Short Short Index Index FingerFinger
DominantDominant
SS or SsSS or Ss
Recessive Recessive
ssss
Long Long Index Index FingerFinger
RecessiveRecessive
ssss
DominantDominant
SS or SsSS or Ss
Height Distribution of Class MembersHeight Distribution of Class Members
HeightHeight MaleMale FemaleFemale TotalTotal
< 150< 150
150-154150-154
155-159155-159
160-164160-164
165-169165-169
170-174170-174
175-179175-179
180-184180-184
185-189185-189
190-194190-194
195-199195-199
Have a partnerHave a partnermeasure your measure your height in cm. height in cm.
We will do a classWe will do a classtally to group the tally to group the data as shown in data as shown in this table. this table.
Genetic Patterns for Blood TypeGenetic Patterns for Blood Type So far we have seenSo far we have seen Alternative PatternsAlternative Patterns
Complete DominanceComplete Dominance CodominanceCodominance
Two alleles per geneTwo alleles per gene Multiple AllelesMultiple Alleles
Codominance: Neither allele masks the other Codominance: Neither allele masks the other
so that effects of both alleles are observed in so that effects of both alleles are observed in heterozygotes without blendingheterozygotes without blending
Multiple Alleles: Three or more alleles exist for Multiple Alleles: Three or more alleles exist for one trait one trait
Note: A diploid individual can only carry any twoNote: A diploid individual can only carry any two of these alleles at once. of these alleles at once.
Multiple Alleles and CodominanceMultiple Alleles and Codominance
ABO Blood Type in HumansABO Blood Type in Humans
Blood TypeBlood Type AlleleAllele
Type AType A AA
Type BType B BB
Type OType O oo
AA == BB > o> o
A and B are codominant.A and B are codominant.AA and B are completely dominant over o.and B are completely dominant over o.
•10%10%
•40%40%
•46%46%
•4%4%
•B or ABB or AB
•A or ABA or AB
•O,AB,O,AB,A,BA,B
(universal)(universal)
•ABAB(universal)(universal)
•B or OB or O
•A or OA or O
•OO
•AB, A,AB, A,B, OB, O
(universal)(universal)
•AA
•BB
•BothBoth
•NeitherNeither
•BB or BoBB or Bo
•AA or AoAA or Ao
•oooo
•ABAB
•OO
•ABAB
•BB
•AA
•FreqFreq•DonatesDonates•Re-Re-
ceivesceives•Anti-Anti-bodiesbodies
•Antigen on RBCsAntigen on RBCs•GenotypeGenotype•TypeType
Human ABO Blood TypesHuman ABO Blood Types
Type A
Type B
A and B
Neither
Codominance is observed for Type AB Blood since the Codominance is observed for Type AB Blood since the
products of both the A and B allelesproducts of both the A and B alleles are found on the cells.are found on the cells.
Paternity Testing before DNA FingerprintingPaternity Testing before DNA Fingerprinting
Type A BloodType A Blood Type O BloodType O Blood
BabyBaby
Type B BloodType B Blood
??
Joan Barry Joan Barry Charlie ChaplinCharlie Chaplin
Possible GenotypesPossible GenotypesAAAAAoAo
Possible GenotypesPossible GenotypesBBBBBoBo
GenotypeGenotypeoooo
XXCan Charlie Chaplin Can Charlie Chaplin be the father?be the father?
Worksheet Worksheet
• Complete pages 99-105 from lab Complete pages 99-105 from lab manualmanual
• Be sure your instructor checks your Be sure your instructor checks your completed worksheet before you leave completed worksheet before you leave the lab. Partial completion will be the lab. Partial completion will be accepted for students who have entered accepted for students who have entered and evaluated all the necessary data and evaluated all the necessary data and attempted some of the genetics and attempted some of the genetics problems. problems.