In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the b hemoglobin alleles in the human gene pool. In the United States, the parasite that causes malaria is not present, but African-Americans whose ancestors were from equatorial Africa are present. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa

directional selection, stabilizing selection

Explanation:

Directional selection is a type of natural selection that favors one extreme phenotype over other phenotypes, thereby modifying allele frequency in the direction of the favored phenotype. This type of positive selection is the main cause of phenotypic diversification. In the USA, the environment created a selection pressure that favored individuals that don't have the defective sickle-cell allele, thereby reducing its frequency in this population. Stabilizing selection, also known as balancing selection, is a type of natural selection where the most common phenotype is selected in the population, thus predominating in future generations. In equatorial Africa, the defective sickle-cell allele is present in a high frequency because individuals that are heterozygous for this allele are less susceptible to malaria, and therefore balancing selection should maintain this allele in the African population.

haploid cells;

answer: although many types of viruses can cause a common cold, rhinoviruses are the most common culprit. a cold virus enters your body through your mouth, eyes or nose. the virus can spread through droplets in the air when someone who is sick coughs, sneezes or talks. theres your answer

explanation: