d. x-linked recessive
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Most genes affecting color vision are carried on the X chromosome. Since males have only one X chromosome, whatever allele, whether defective or normal, that is present on the X chromosome and not on the Y chromosome gets expressed. Mutations in the genes that govern color vision cause the individual to not be able to detect certain colors. Males are affected by colorblindness more often than females. Females become colorblind only if both X chromosomes carry the defective allele for detecting a certain color. If females are heterozygous for the defective allele, their vision is normal.