1. ABO Blood Groups and Genetic Disorders
Human Inheritance
ABO Blood Groups and Genetic Disorders

2. Important Vocabulary
Slide # 2
1. Carrier: someone who is heterozygous for a trait
2. Multiple alleles: traits that have more than 2 possible alleles; still only inherit 2 alleles
3. Co-dominance: when two different alleles are present and BOTH alleles are expressed.
4. Mutation: a change in an organism’s DNA; changes how a gene functions
a. leads to 2 or more alleles for a given trait

3. ABO Blood Groups 1. Multiple alleles
Slide # 3
ABO Blood Groups
1. Multiple alleles
a. 3 different alleles; IA, IB, & i
b. 6 genotypes / 4 phenotypes
IA IA or IA i = Type A
IB IB or IB i = Type B
IA IB = Type AB
i i = Type O
2. IA and IB are co-dominant; both are expressed if both are present
Type O is the universal donor
Type AB is the universal receiver

4. Genetic Disorders are caused by defective genes.
Defective genes arise from mutations in DNA.

5. Cystic Fibrosis
Slide # 5
1. Mode of inheritance: recessive allele on chromosome # 7
2. Symptoms:
a. abnormally thick mucus forms on outside of cells
b. lung & pancreas cells most seriously affected
c. have frequent lung infections
d. mucus blocks ducts of pancreas; can’t digest food properly
3. Newborns can be tested
4. Life expectancy: about years old
5. Carriers are resistant to typhoid (caused by a Salmonella bacterium) and cholera
1 in 25 Caucasians in US are carriers
1 in 2500 are affected

6. PKU 1. Mode of Inheritance: recessive allele on chromosome # 12
Slide # 6
PKU
1. Mode of Inheritance: recessive allele on chromosome # 12
2. Symptoms
a. body cannot break down phenylalanine
b. phenylalanine builds up in the blood & poisons nerve cells
c. Untreated babies develop severe brain damage (mental retardation)
Easily treated by following strict diet that avoids phenylalanine
All newborns are tested for PKU
Female carriers have a much lower likelihood of miscarriage
Foods farthest away from the target must be avoided.

7. 8 to 10% African Americans are carriers
Sickle-Cell Anemia
Slide # 7
1. Mode of inheritance: recessive allele on chromosome # 11
2. Symptoms
a. hemoglobin doesn’t form correctly
b. blood cells become sickle shaped
c. sickle shaped cells get stuck in blood vessels
d. sickle shaped cells don’t carry O effectively – causes pain & damage to organs
3. Affected persons live to be about 50
4. Most states test newborns with a simple blood test
5. Carriers are resistant to malaria
Normal blood cells live 120 days
Sickle-shaped cells live 20 days
8 to 10% African Americans are carriers

8. Tay Sachs 1. Mode of Inheritance
Slide # 9
Tay Sachs
1. Mode of Inheritance
a. recessive allele on chromosome # 15
2. Symptoms
a. Fatty substance builds up in nerve cells in brain
b. Gradual paralysis & loss of nerve function
c. Affected children die by age 4 or 5
3. Carriers resistant to tuberculosis
11% of Jewish population are carriers
Also common in French-Canadians & Cajuns

9. Huntington’s Disorder
Slide # 8
1. Mode of inheritance: dominant allele on chromosome # 4
2. Why the person become affected:
a. Affected individuals have 40 or more “CAG” repeats in the gene
b. codes for an excessive amount of glutamine (amino acid) in the protein
c. the protein clumps in the brain and destroys nerve cells in the basal ganglia
3. Symptoms
brain cells slowly deteriorate; jerking muscles, slurred speech, difficulty swallowing, loss of balance, reasoning & memory loss
Death occurs 15 – 20 years after symptoms appear
4. Symptoms usually begin at years of age

10. Sex-Linked Disorders
Sex-linked traits: Genes located on the sex chromosomes.

11. Slide # 10
Sex Linked Traits
1. Sex-linked trait: A trait that is determined by a gene found on the X chromosomes.
2. Occur more often in males because males only receive one X chromosome (one copy of the gene).
3. Fathers pass the X chromosome on to daughters only.
4. Mothers pass an X chromosome on to sons and daughters.
5. Females must receive 2 copies of the defective gene to show the trait.
What is the gender of this individual?
XY = male

12. Duchenne Muscular Dystrophy
Affects production of dystrophin (a protein in muscle)
Symptoms
a. Fatigue
b. Mental retardation
c. Muscle weakness; confined to wheelchair by age 12
d. Rapidly worsening form of muscular dystrophy
e. Death by age of 25 usually because of lung disorder (pneumonia)
3. Affects 1 in 3,600 male infants

13. Hemophilia A 1. Mode of inheritance: recessive allele on X chromosome
Slide # 11
1. Mode of inheritance: recessive allele on X chromosome
2. Main Symptom
a. inability to produce a workable form of coagulation factor VIII; needed to clot blood
b. prolonged bleeding or oozing after an injury, surgery, etc.
c. bleed internally – especially at the knees and elbows and other joints
3. Without clotting factors, the individual could die from losing too much blood
Hemophilia can be traced through a pedigree of the royal family.

14. Color-blindness
Slide # 12
1. Mode of Inheritance: recessive allele on X chromosome
2. Symptoms
a. inability to distinguish red and green colors
b. Normal life span