Answer:
The sickle-cell allele is widely known as a variant that causes red blood cells to be deformed into a sickle shape when deoxygenated in AS heterozygotes, in which A indicates the non-mutant form of the β-globin gene, and also provides resistance to malaria in AS heterozygotes.
Explanation:
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a chemical landfill is where chemical waste is stored once it has been used
if it is secure it means that the waste cannot pollute the environment through water, air etc
