Can heterozygous for sickle cell have greater resistance?

Yes, individuals who are heterozygous for the sickle cell trait (having one normal hemoglobin allele and one sickle cell allele) can have greater resistance to malaria. The presence of the sickle cell allele provides some protection against the malaria parasite, as the altered shape of the red blood cells makes it less hospitable for the parasite to thrive. This selective advantage is particularly observed in regions where malaria is endemic, leading to a higher prevalence of the sickle cell trait in those populations.