The genotypes for both parents are DD and DD for a genetic trait. Their children all have a genetic disorder. Which genetic disorder do they most likely have?

The disease hemophilia is caused by a single gene that is located on the X chromosome. Because human females have two X chromosomes (XX), they have two copies of this gene. Since hemophilia is recessive (h), a female must have two copies of the recessive allele to have the disease.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".