Question

1.

Explain how some patients who are homozygous for the sickle-cell allele do not develop sickle-cell crisis or other symptoms of the disease.

Because of a mutation to a regulatory gene, a variant form of the beta subunit is expressed that does not cause sickling of hemoglobin protein. Because of a defective regulatory gene, fetal hemoglobin is expressed in adulthood which compensates for defective adult hemoglobin. Because of an additional mutation to the gene for the beta subunit of hemoglobin, the sickling of hemoglobin protein is much less likely to occur. Because of a mutation to the fetal hemoglobin gene, fetal hemoglobin does not turn off during adulthood and the defective beta unit of hemoglobin is not expressed.

2.	Identify symptoms of sickle-cell anemia. Select the TWO answers that are correct.
	hyperactivity and inability to concentrate presence of crescent-shaped red blood cells pain, shortness of breath, and fatigue excessive glucose in the urine

3.	How might gene editing lead to treatments for sickle-cell anemia? Select the TWO answers that are correct.
	repairing the defective version of the hemoglobin gene in patients using a viral vector inserting a healthy version of the hemoglobin gene into patients using a viral vector disabling the regulatory gene that represses expression of fetal hemoglobin after birth modifying the sequence of hemoglobin genes so that only alpha subunits are needed

Answer 1

Q.1 Ans B - Because of a defective regulatory gene, fetal haemoglobin is expressed in adulthood which compensates for defective adult haemoglobin

Q.2. Ans : Presence of crescent-shaped red blood cells

Pain, shortness of breath and fatigue

Q.3 Inserting a healthy version of the hemoglobin gene into patients using viral factor

Disabling the regulatory gene that represses expression of fetal hemoglobin after birth