Question

0.5 pts
sickle cell anemia is caused by a missense mutation in the β - globin gene. the normal allele of the β - globin gene is located near the left end of chromosome 2. if someone has one normal allele and one mutant allele, where are they located?
hint: draw out each answer choice so you understand what each is saying.
one is located on the left end of one chromosome 2, the other is on left end of the homologous chromosome.
one is located on the left end of one chromatid of chromosome 2, the other is on the left end of the other sister chromatid.
one is located on the left end of chromosome 2, the other is on the left end of a non - homologous chromosome.
one is located on the left end of chromosome 2, the other is located on the right end of the homologous chromosome.
one is located on the left end of one chromatid of chromosome 2, the other is located on the right end of the other sister chromatid

Explanation:

In humans, each chromosome has a homologous pair. Genes for the same trait (like the β - globin gene here) are located at the same locus on homologous chromosomes. Since the normal allele is on chromosome 2 (left - end), the mutant allele (as it's an allele of the same gene) will be on the homologous chromosome 2 at the same (left - end) locus. Sister chromatids are identical copies (assuming no crossing - over in the case of normal replication, and alleles are different here, so not sister chromatids). Non - homologous chromosomes carry different sets of genes. Different ends (left and right) of a chromosome would have different genes.

Answer:

One is located on the left end of one chromosome 2, the other is on left end of the homologous chromosome.