1. Human Genetics
By Diana Bivens

2. Autosomal Recessive Disorders
Autosomes: chromosomes 1-22
many disorders are autosomal recessive
Requires defective recessive allele to be passed by BOTH parents
Probability of offspring having the disorder: 25% if both parents are carriers/ 0 if only one parent is a carrier.

3. Cystic Fibrosis (CF) 1 in 20 Caucasians are carriers
Rate of occurrence: 1 in 2000
Characteristics: accumulation of mucus in lungs and digestive tract.
Life expectancy depends on severity of disease and quality of treatment
Many die from lung
failure

4. Cystic Fibrosis

5. Phenylketonuria (PKU)
Metabolic disorder in which phenylalanine cannot be broken down
Rate of occurrence: 1 in 15,000
Can result in mental retardation
All infants in US are screened
Reducing intake of phenylalanine until puberty can prevent retardation

6. PKU

7. Tay-Sachs Disease Metabolic disorder that affects the nervous system
More common in those of Central and Eastern European Jewish descent
1 in 30 are carriers
Life expectancy: ~5 years

8. Tay Sachs Disease

9. Sickle cell anemia Disorder of the Red Blood Cells
Causes sickling of cells preventing normal function
Lack of oxygen to organs can cause
tissue damage resulting in intense pain
Affects mostly those of African descent
1 in 12 African-Americans are carriers
>70,000 have the
disease

10. Sickle Cell Anemia

12. Fugates of Appalachia

13. Autosomal Dominant Disorders
Requires only ONE allele for the disorder to be passed
Probability of having offspring with the disorder: 50% if one parent has the defective allele

14. Huntington’s Disease Results in damage to the brain
Symptoms generally occur after the affected reaches 30 years old
Many have children before they show symptoms
Rate of Occurrence: 1 in 15,000
Life expectancy: years after onset of symptoms
Genetic screening can identify those affected before the onset of symptoms

15. Huntington’s Disease

16. Achondroplasia Results in dwarfism
If a child inherits two copies of the dominant gene, it can be fatal.
Not all types of dwarfism are caused by a dominant gene.

17. Sex-Linked Inheritance
Alleles that are inherited on the sex chromosomes
Written as superscripts on the X and Y chromosomes
XªX or XªY
Most sex-linked traits are associated with the female (X) chromosome

18. Red-Green Color Blindness
Disorder in which a person cannot differentiate between red and green
Allele passed on the X chromosome
Disorder more common in males
Males: one copy results in color blindness
Females: one copy (carrier)
two copies result in color blindness

19. Red-Green Color Blindness

20. Hemophilia Disorder that prevents blood from clotting properly
Allele passed on the X chromosome
Males more commonly affected
males: one copy results in disorder
Females: one copy (carrier)
two copies results in disorder

21. Hemophilia

22. Multiple Alleles Many traits are controlled by more than two alleles
ex. Fur color in many animals

23. Polygenic Inheritance
when traits are controlled by two or more genes
ex. Hair color, eye color, skin color, height, fingerprint patterns

24. Blood Types An example of several different hereditary patterns
Multiple alleles: A, B, and O
Codominance: A and B
Recessive and Dominant:O is recessive to both A and B

25. Blood Types
*Notice how
the genotype
is written for
each type

27. Blood Transfusion Facts
People with type O- blood can donate to anyone (universal donor), but can only receive type O- blood.
People with type AB+ blood can receive blood from anyone (universal recipient), but can only donate to someone who is type AB+.

28. Mrs. Bivens’s Public Service Anouncement
You CAN NOT contract HIV, Hepatitis, or any other communicable disease by donating blood
You CAN save a life by donating

29. Environmental Influences on Heredity
External factors can influence expression of genes
ex. Genes code for potential height/nutrition can affect the outcome

30. Environmental Influences
Hormone differences between the sexes can affect gene expression
Ex. balding/ the allele is thought to be dominant in males and recessive in females