The term 'heterozygote advantage' describes the case in which the heterozygous genotype of individuals within a population confers a higher relative fitness than either the homozygous dominant or homozygous recessive genotype. Which of the following is an example of a condition in which the heterozygote genotype confers a higher relative fitness?
1) Sickle cell anemia
2) Huntington's disease
3) Cystic fibrosis
4) Color blindness