Final answer:
Each chromosome 11 carries one allele for the β-globin gene, and since humans have two copies of chromosome 11, the total number of β-globin alleles on chromosome 11 in a human is two.
Step-by-step explanation:
The question involves understanding the inheritance of the β-globin gene on chromosome 11. Humans have two copies of chromosome 11, one inherited from each parent. Each chromosome 11 carries one allele for the β-globin gene. Thus, the total number of β-globin alleles on chromosome 11 in a human is two.
These alleles can be the same in both chromosomes (homozygous), or different (heterozygous), contributing to genetic diversity and the possibility of disorders like beta-thalassemia when mutations occur in both alleles.