Joseph and Kenneth are twins resulting from two ova. What proportion of their genes do the boys have in common?

Which of the following symptom(s) is/are characteristic of children with Rett's disorder but

not characteristic of children with autism or with Asperger's disorder? a. An initial period of normal development b. Stereotypical hand movements, such as hand-wringing c. Loss of interest in social interactions d. Communication difficulties or oddities e. b and c

Which is sometimes caused or aggravated by a mother's illness or malnutrition during pregnancy?

a. Sleep apnea b. Schizophrenia c. Anorexia nervosa d. Parkinson's disease