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 Dominant allele masks other alleles Recessive allele is masked Locus 1 Locus 2 Locus 3

Genotype and Phenotype Term Definition Example Genotype Alleles carried by an individual All diploid individuals have two copies of each allele homozygous = both alleles are the same heterozygous = two different alleles EE, Ee, ee Phenotype Physical characteristic or appearance of an individual free or attached earlobe

Earlobe Attachment Genotype Phenotype EE or Ee E is dominant over e Free earlobe ee Attached Earlobe

Solving Genetics Problems Convert parental phenotypes to genotypes --may need to use info about grandparents or children already born to complete these genotypes Use Punnett Square to determine genotypes of offspring Convert offspring genotypes to phenotypes

Genetics Problem 6, p. 104 ee Ee George has attached ear lobes. Laura has free earlobes, but she is heterozygous for this trait. What are the chances of their child having free earlobes? Genotype for George Genotype for Laura ee Ee

Homozygous parents can only pass one form of an allele to their offspring.

Heterozygous parents can pass either of two forms of an allele to their offspring.

Genetics Problem 6, p. 104 ee Ee E e e Ee ee Ee ee George has attached ear lobes. Laura has free earlobes, but she is heterozygous for this trait. What are the chances of their child having free earlobes? Genotype for George Genotype for Laura ee Ee E e e Ee ee 50% free earlobes 50% attached earlobes Ee ee

Genetics Problem 16, p. 105 EeHh EeHh Genotype for Willy Both Willy and Ethyl are heterozygous for earlobe attachment and also for hitchhiker’s thumb. What are the chances of a child with… …attached earlobes and a hitchhiker’s thumb? …free earlobes and no hitchhiker’s thumb? Genotype for Willy Genotype for Ethyl EeHh EeHh EH Eh eH eh EH Eh eH eh

EH Eh eH eh EEHH EEHh EeHH EeHh EH Eh eH eh EEHh EEhh EeHh Eehh EeHH …attached earlobes and a hitchhiker’s thumb? eehh = 1/16 …free earlobes and no hitchhiker’s thumb? E_H_ = 9/16

Lab Today Simple Inheritance (12 traits) The “Which Classmate Shares the Most Traits with You?” Game: Four student volunteers – single elimination “Direct Comparisons with Individuals” – four classmates and find % of traits shared Complex Inheritance: Height, ABO blood type Solving Genetics Problems with Punnett squares

Simple Inheritance Trait Your Phenotype Your Genotype Bent little finger Not bent or BB or Bb (list any ONE genotype that fits) bb Determine your phenotype and potential genotype for each trait. At a specified time, your instructor will conduct a class tally for all traits.

Direct Comparisons with Individuals Your Phenotype 1st person 2nd person attached earlobe 20% -- widow’s peak hitchhiker’s thumb pigmented iris long index finger % Traits Shared 60% 40%

Sex-Influenced Traits Change Dominance Pattern by Gender Males Females Short Index Finger Dominant SS or Ss Recessive ss Long Index Finger Recessive ss

Height Distribution of Class Members Male Female Total < 150 150-154 155-159 160-164 165-169 170-174 175-179 180-184 185-189 190-194 195-199 Have a partner measure your height in cm. We will do a class tally to group the data as shown in this table.

Genetic Patterns for Blood Type So far we have seen Alternative Patterns Complete Dominance Codominance Two alleles per gene Multiple Alleles Codominance: Neither allele masks the other so that effects of both alleles are observed in heterozygotes without blending Multiple Alleles: Three or more alleles exist for one trait Note: A diploid individual can only carry any two of these alleles at once.

Multiple Alleles and Codominance ABO Blood Type in Humans Blood Type Allele Type A A Type B B Type O o A = B > o A and B are codominant. A and B are completely dominant over o.

Human ABO Blood Types Type Genotype Antigen on RBCs Anti- bodies Re- ceives Donates Freq A AA or Ao Type A B A or O A or AB 40% B BB or Bo Type B A B or O B or AB 10% AB AB A and B Neither AB, A, B, O (universal) AB (universal) 4% Figure: TABLE 12.1 Title: Human blood group characteristics Caption: O oo Neither Both O O,AB, A,B (universal) 46% Codominance is observed for Type AB Blood since the products of both the A and B alleles are found on the cells.

Paternity Testing before DNA Fingerprinting Joan Barry Charlie Chaplin Type A Blood Type O Blood ? Possible Genotypes AA Ao Genotype oo Baby Type B Blood Possible Genotypes BB Bo X Can Charlie Chaplin be the father?

Worksheet Complete pages 99-105 from lab manual Be sure your instructor checks your completed worksheet before you leave the lab. Partial completion will be accepted for students who have entered and evaluated all the necessary data and attempted some of the genetics problems.