1. Page 3 left Column

2. Types of Complex Inheritance
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic Traits

3. Incomplete dominance Both alleles partially show by blending together
Analogy: Mixing Together Paint
Blue
Green
Yellow

4. Both alleles are completely expressed at the same time.
codominance
Both alleles are completely expressed at the same time.
-Analogy: Mixing Together Pebbles
Yellow AND Blue
Yellow
Blue

5. Multiple alleles Having more than two alleles for a specific trait
Ex. An example is blood groups in humans. Blood type, for example, is determined by three alleles.
A is codominant IA
B is codominant IB
O is recessive i

6. Blood Types Alleles (Genotype) Blood Type (Phenotype)
AA or Ao IAIA or IAi
Type A
BBor Bo IBIB or IBi
Type B
AB only IAIB
Type AB
oo only ii
Type O

7. Polygenic Traits
Traits that are determined by the interaction of multiple pairs of genes
Ex: skin color, height

8. Page 4 left Column

9. Multiple Allele Traits: Blood Type
Blood type exhibits codominance and multiple alleles. The chart below shows the phenotype and genotype of blood types.
Phenotype Genotype
Type A AA or Ao IAIA or IAi
Type B BB or Bo IBIB or IBi
Type AB AB IAIB
Type O oo ii
Blood Type is controlled by 3 alleles: A, B, O. A & B are codominant, O is recessive.

10. 1. a) What are the two genotypes possible for a person who as A blood
1. a) What are the two genotypes possible for a person who as A blood? IAIA or IAi
b) What genotype does a person with AB blood have? IAIB
c ) What genotype does a person with O blood have? ii d) What are the two genotypes possible for a person who as B blood? IBIB or IBi

11. Page 5 left Column

12. Sex-Linked

13. Which Chromosome Determines our Sex?
Introduction: A human has 23 pairs of homologous chromosomes
Pairs 1-22 are called Autosomes – chromosomes not involved in determining sex
Pair 23 – Sex Chromosomes

14. How is Sex Determined? Sex chromosomes are X and Y Females are XX
Males are XY

15. How is Sex Determined?
Females can only make eggs with the X chromosome
Males make sperm with the X or Y chromosome, so it is the male that determines the sex of a baby

16. How is Sex Determined?
50% chance male
50% chance female

17. Discovery of Sex-Linked Genes
Discovered in fruit flies (drosophila melanogaster) by Thomas Hunt Morgan

18. Discovery of Sex-Linked Genes
Eye color is sex-linked in fruit flies. He discovered that alleles for eye color is carried on the X chromosome ONLY!
NO ALLELES ON THE Y CHROMOSOME

19. Why Fruit Flies? Easy to maintain 10 – 15 day life cycle
Many offspring produce in a short time

20. Sex-Linked Traits Traits that are controlled by the sex chromosomes
Colorblindness – can’t see the difference between certain colors
Hemophilia – blood does not clot properly

21. Example H = Normal h = hemophilia
Important Rule: Only write the gene over the X chromosome

22. Female Genotypes XHXH : Normal Female (Homozygous Dominant)
XHXh : Normal Female Carrier (Heterozygous)
XhXh : Female with hemophilia (Homozygous Recessive)

23. Male Genotypes XHY : normal male without hemophilia
XhY : male with hemophilia

24. Sex-linked traits occur more in males than females because
Males only need one “bad” gene on the X chromosome
But females need two “bad” genes on both X chromosomes