Question

The mutation resulting in the allele for sickle–cell anemia removes a restriction site from the β–globin gene such that a specific probe hybridizes to one 1.3–kb fragment instead of two fragments of 1.1 kb and 0.2 kb. What restriction pattern will be seen in sickle–cell carriers?

Answer 1

Sickle-cell carriers will exhibit a combined restriction pattern on gel electrophoresis, displaying both a 1.3-kb fragment and two fragments of 1.1 kb and 0.2 kb due to the presence of both normal and mutated alleles.

Step-by-step explanation:

The sickle-cell carriers, also known as individuals with sickle-cell trait, carry one allele for the normal hemoglobin (A) and one allele for the sickle-cell hemoglobin (S). Due to the presence of both alleles, their restriction pattern will show a combination of the patterns seen in homozygous normal and homozygous sickle-cell individuals.

Therefore, a DNA sample from a carrier subjected to restriction enzyme digestion followed by gel electrophoresis will reveal both a 1.3-kb fragment (due to the sickle cell allele which lacks a restriction site) and two fragments of 1.1 kb and 0.2 kb (due to the normal allele with the intact restriction site). However, in carriers of the sickle-cell allele, one of the restriction sites is lost, resulting in one larger fragment of 1.3 kb.