The following is a diagram that presents a pedigree of a family affected by Danon disease, a condition that causes a malfunction of the heart. Filled circles and squares represent affected individuals, while open circles and squares represent phenotypically unaffected individuals. A family tree diagram. At the top are the pair open square and filled circle. On the branch below are 4 pairs: filled circle and open square, open circle and open square, open square and open circle, filled square and open circle. Below filled circle and open square are filled circle, filled square, open circle, open square. Below open circle and open square open circle and open square. Below open square and open circle are open circle and open square. Below filled square and open circle are 4 filled circles and 4 open squares.

What is most likely true about the disease-causing allele?

It is X-linked dominant.
It is X-linked recessive.
It is autosomal dominant.
It is autosomal recessive.