A genetic test for sickle-cell disease uses restriction enzymes that cut the normal beta-globin allele but not the sickle (HbS) allele. The gel below shows results for four family members along with a size ladder.
Which children are heterozygous (carriers)?
- A
Both children are heterozygous.
- B
Only C1 is a carrier.
- Ccheck_circle
Both parents are heterozygous; C1 is HbS/HbS and C2 is HbA/HbA.
- D
C1 and C2 are both unaffected and homozygous normal.
Explanation
Both parents show two bands (1.3 uncut and 0.7 cut), indicating heterozygotes. C1 shows only the 1.3 uncut band (HbS/HbS); C2 shows only the 0.7 cut band (HbA/HbA).