1. What’s Your Blood Type? A B AB O

2. Multiple Alleles
Many genes have more than two alleles.
This does NOT mean that an individual can HAVE more than two alleles.
This simply means that more than two alleles for a trait exist in a population.

3. Multiple Alleles: Example
Human blood type is controlled by multiple alleles: A, B, O.
O is recessive, while A and B are codominant, so if both alleles are present, both are expressed.
There are four possible blood types: A, AB, B, and O.

4. Multiple Alleles

5. What happens if we get the wrong blood from a blood donor?

11. Sex-Linked Traits and Chromosomes
Autosomes are the “normal” or body chromosomes
Sex chromosomes (X or Y) contain sex-linked genes

12. Sex-Linked Traits and Chromosomes
Specific pairs of these sex chromosomes are what determine our sex. The genes on each chromosome code for proteins that help us develop biologically into males or females.
Males have the sex chromosomes XY .
Females have the chromosomes XX.

13. Sex-Linked Traits and Chromosomes

15. Sex-Linked Traits and Chromosomes
We get 1 X from mom, and either 1 X or 1 Y from dad, so there is ALWAYS a chance of being a boy or girl. Which parent determines the gender of the offspring?
The dad.

16. X-Linked Traits and Disorders
X-linked traits are inherited through genes on the X chromosome.

17. X-Linked Traits and Disorders
X-linked disorders are more common in males than in females. Why?
Males have only one X chromosome.
If the X chromosome carries a defective allele for a gene, the Y chromosome does not have a normal allele that is able to balance it out.
This results in a genetic disorder.

18. X-Linked Traits and Disorders
If the X chromosome carries a defective allele for a gene, the Y chromosome does not have a normal allele that is able to balance it out.

19. X-Linked Traits and Disorders
X-linked traits are usually passed down through the mom. Why?
Mothers can pass the genes to daughters AND sons
Fathers can pass genes to daughters BUT NOT to sons

20. Examples of X-Linked Disorders
Colorblindness
Decreased ability to see or distinguish between certain colors
Red-green colorblindness, blue-yellow colorblindness

21. Examples of X-Linked Disorders
Colorblindness
Decreased ability to see or distinguish between certain colors
Red-green colorblindness, blue-yellow colorblindness

22. Examples of X-Linked Disorders
Hemophilia
A bleeding disorder that prevents blood from clotting properly
The person bleeds more than someone without hemophilia

23. Examples of X-Linked Disorders
Duchenne Muscular Dystrophy
A disorder that involves rapidly increasing muscle weakness and loss of muscle tissue

24. Blood Type/Multiple Allele Practice Problems…

25. Pedigrees
A diagram that shows the inheritance pattern of a trait over many generations is called a pedigree.

26. I II III How To Read A Pedigree Pedigree Symbols Male Female
Children/ Marriage Siblings
III

27. How To Read a Pedigree
Looking at a family pedigree, we observe how certain traits have been passed down from parents to offspring and also how certain traits and genetic disorders are expressed.

28. Tips for interpreting pedigree
1. How many males vs. females are affected?
Equal = autosomal
More males = sex-linked
2. Does it skip generations?
Yes = recessive, No = dominant
3. Who is a carrier (unaffected)?
females only = sex-linked
either sex = usually autosomal

29. Autosomal Recessive Inheritance
1. Males and females are equally affected
2. May skip generations or appear to be an isolated event
3. Chance of offspring having trait is ¼ if two parents are heterozygous carriers

30. Autosomal dominant Inheritance
1. Males and females are equally affected
2. Every affected person has an affected biological parent (no skipping generations)
3. Normal siblings do not pass trait on to their offspring

31. X-Linked Recessive Inheritance
1. Males affected more than females
2. May skip generations (ex. grandfather to grandson), but all affected males inherit trait from carrier mothers
3. The disease is never passed father to son– mothers are carriers.

32. X-Linked Inheritance: A Case Study