Question

what mutation causes sickle-cell anemia?
○ adenine replaces thymine
○ thymine replaces adenine
○ guanine replaces cytosine
○ guanine replaces thymine
○ cytosine replaces adenine

Explanation:

Sickle - cell anemia is caused by a point mutation in the HBB gene. In this mutation, the DNA sequence change is from GAG to GTG. At the DNA base - pair level, this corresponds to adenine (A) replacing thymine (T) in the template strand. This single - base substitution leads to a change in the amino acid sequence of the beta - globin protein (valine replaces glutamic acid), which causes the abnormal sickling of red blood cells.

Answer:

adenine replaces thymine