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

2. 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

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

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

5. 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

6. 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

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

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

9. 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

10. 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

11. 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

12. 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

13. 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.

14. 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%

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

16. Height Distribution of Class Members
Male
Female
Total
< 150
Have a partner measure your height in cm.
We will do a class
tally to group the
data as shown in this table.

17. 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.

18. 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.

19. 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.

20. 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?

21. 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.