Males XY—presence of the Y chromosome determines male sex
Child’s Genotype Child’s Phenotype
Regulator genes control other genes (puberty, graying hair)
Inheritance patterns are complicated with few following Mendel’s simple pattern
Mendelian inheritance patterns Above are the Mendelian inheritance patterns for two brown-haired parents who are both heterozygous for hair color. The allele for brown hair (B) is dominant, and that for blond hair (b) is recessive. Note that these parents have three chances out of four of producing children with brown hair. They have two chances in four of producing brown-haired children who carry the gene for blond hair.