Easy· Genetic Disorders (Pedigree Analysis)· +4 / −1
Which one of the following symbols represents mating between relatives in human pedigree analysis?
*Options (symbols, described from the figure):*
(1) A filled square, a filled circle and a filled diamond.
(2) An open square joined to an open circle by a single horizontal line.
(3) An open square joined to an open circle by a *double* horizontal line.
(4) An open square joined to an open circle by a horizontal line, with a vertical line descending from it to a filled square.