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Human Genetics Lab Human Genetics Lab When Students Are the When Students Are the Subjects…… Subjects……

Human Genetics Lab

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Human Genetics Lab. When Students Are the Subjects……. Loci, Genes and Alleles. Locus = area on chromosome where gene is located (plural = loci) Gene = sequence of DNA that codes for a protein, gives rise to physical trait Alleles = alternative forms of a gene - PowerPoint PPT Presentation

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Page 1: Human Genetics Lab

Human Genetics Lab Human Genetics Lab

When Students Are the Subjects…… When Students Are the Subjects……

Page 2: Human Genetics Lab

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

Page 3: Human Genetics Lab

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

Page 4: Human Genetics Lab

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

Page 5: Human Genetics Lab

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

Page 6: Human Genetics Lab

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

Page 7: Human Genetics Lab

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.

Page 8: Human Genetics Lab

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.

Page 9: Human Genetics Lab

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

Page 10: Human Genetics Lab

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

Page 11: Human Genetics Lab

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

Page 12: Human Genetics Lab

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

Page 13: Human Genetics Lab

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.

Page 14: Human Genetics Lab

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%

Page 15: Human Genetics Lab

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

Page 16: Human Genetics Lab

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.

Page 17: Human Genetics Lab

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.

Page 18: Human Genetics Lab

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.

Page 19: Human Genetics Lab

•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.

Page 20: Human Genetics Lab

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?

Page 21: Human Genetics Lab

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.