1. Natural Selection in Human Populations
Natural Selection and Disease
The CCR5 gene
Gene is transcribed and translated to a surface protein of T-helper cells.
Related to HIV (human immunodeficiency virus
Virus acquired from chimpanzees ca. 1930
Does no harm in chimpanzees.
Related to AIDS (acquired immune deficiency syndrome)

2. Prevalence of HIV infection, ages 15-45

3. Increase over time in HIV prevalence in adults

4. Life cycle of
HIV

5. Azidothymidine (AZT)
treatment

6. Fast acquisition of resistance to
AZT

7. Some people are resistance to HIV
CCR5 – delta 32 allele

9. Sickle cell anemia and malaria
Global incidence of malaria: cases/year
1-3 million deaths/year
Hemoglobin
HbA  HbS
HbA/HbS = heterozygote advantage

10. HbA/HbS
sickle cell trait
HbS/HbS
sickle cell anemia

11. Frequency of HbS

12. Prevalence of
malaria

13. Relationship between HbS and
malarial impact