Write the likelihood function for males and females together.
Color blindness is due to a recessive allele that appears on the X chromosome. If the color blindness allele has frequency p, a fraction p of males will show the phenotype, and a fraction p2 of females will show the phenotype (because they require two copies). We wish to estimate the fraction p from a sample of 1000 males, 90 of whom are color-blind, and 1000 females, 13 of whom are color-blind.