Use the Following to Answer Questions
You Are Studying Epigenetic

Use the following to answer questions
You are studying epigenetic regulation of the Bdnf gene in mice and its association with memory. You train mouse B to avoid an adverse stimulus and then isolate genomic DNA from its brain. Mouse A is untrained and used as a control. You take the brain DNA samples and split each of them into two parts. One part is treated with sodium bisulfite and the other part is left untreated. You then perform PCR for the Bdnf locus and digest the PCR product with the restriction enzyme AccII that cuts DNA at the sequence CGCG. The digested DNA is then separated by agarose gel electrophoresis to obtain the following DNA fragments:
$$\begin{array}{l}\begin{array} { c c } \text { Mouse A (Bisulfite DNA) } & \text { Mouse A (Untreated DNA) } \\\hline 21.2 \mathrm {~kb} & 19.3 \mathrm {~kb} \\7.4 \mathrm {~kb} & 7.4 \mathrm {~kb} \\5.8 \mathrm {~kb} & 5.1 \mathrm {~kb} \\5.7 \mathrm {~kb} & 3.9 \mathrm {~kb} \\4.9 \mathrm {~kb} & 3.5 \mathrm {~kb} \\3.5 \mathrm {~kb} & 2.7 \mathrm {~kb} \\& 2.2 \mathrm {~kb} \\& 1.9 \mathrm {~kb} \\& 1.8 \mathrm {~kb} \\& 0.7 \mathrm {~kb}\end{array}\\\\\begin{array} { c c } \text { Mouse B (Bisulfite DNA) } & \text { Mouse B (Untreated DNA) } \\\hline 19.3 \mathrm {~kb} & 19.3 \mathrm {~kb} \\7.4 \mathrm {~kb} & 7.4 \mathrm {~kb} \\5.7 \mathrm {~kb} & 5.1 \mathrm {~kb} \\5.1 \mathrm {~kb} & 3.9 \mathrm {~kb} \\4.9 \mathrm {~kb} & 3.5 \mathrm {~kb} \\3.5 \mathrm {~kb} & 2.7 \mathrm {~kb} \\1.9 \mathrm {~kb} & 2.2 \mathrm {~kb} \\0.7 \mathrm {~kb} & 1.9 \mathrm {~kb} \\& 1.8 \mathrm {~kb} \\& 0.7 \mathrm {~kb}\end{array}\end{array}$$
-How many of the AccII sites were methylated at the Bdnf locus in the untrained mouse?

A) 1
B) 2
C) 3
D) 4
E) 5