Pedigree of Red-Green Colorblindness

Pedigree of Red-Green Colorblindness

Individual II-1: Unaffected

Genotype: XCXC Phenotype: NormalWe know that this woman is homozygous dominant, but we do not exactly know her mother's genotype. She could be XCXC or XCXc, but her father would have to be XCY. We know this because if he were affected, she would be either a carrier for the allele or be colorblind.

Individual III-5: Affected

Genotype: XcXc Phenotype: Colorblind Individual III-5 is the proband in this pedigree. She is confused about how she became colorblind because she knows that red-green colorblindness is much more prominent in males. Her father and brother are both affected, but her sister and mother are not. She now wonders why she is the only colorblind woman in her family besides her grandmother on her father's side.

Possible Offspring

Genotype Possibilities: XCXc: XcXc: XcY 1:1:2 Phenotype Possibilities: Normal: Colorblind 1:3 If she were to have offspring with an unaffected male, her daughters would be carriers and her sons would be colorblind. If she were to have offspring with a colorblind male, her children could only be colorblind.

Individual III-8: Affected

Genotype: XcY Phenotype: Colorblind This man's mother, as a carrier, could have passed down either her dominant or recessive allele. He obtained the recessive allele causing him to be colorblind.

Individual I-1: Unaffected

Genotype: XCY Phenotype: NormalThis man has a normal phenotype meaning that he is not colorblind.

Individual III-2: Carrier

Genotype: XCXc Phenotype: Normal This woman is heterozygous. Her father gave her the recessive allele, and the dominant allele from her mother masked the recessive one.

Individual III-9: Unaffected

Genotype: XCY Phenotype: Normal This man is not colorblind because he inherited the dominant allele from his carrier mother.

Individual II-2: Affected

Genotype: XcY Phenotype: Colorblind This man is affected, and he inherited this trait from his mother. In X-linked recessive traits, an affected mother will always have affected sons because she can only give them her recessive allele.

Individual II-5: Carrier

Genotype: XCXc Phenotype: Normal This woman became a carrier because her mother was unaffected, so she passed on her dominant allele. Her father was affected, so he passed on his recessive allele.

Individual III-6: Unaffected

Genotype: XCY Phenotype: Normal Because his mother is a carrier, this man had a 50% chance of being colorblind. Since his mother passed on her dominant allele, though, he is unaffected.

Individual III-1: Unaffected

Genotype: XCY Phenotype: Normal This man has a normal phenotype because his mother is unaffected, so she passed down her normal allele(XC). His father is affected, but he only passed down his Y chromosome to his son.

Individual III-3: Carrier

Genotype: XCXc Phenotype: Normal This woman is a carrier for red-green colorblindness, so she is heterozygous. She had a 1:1 chance of being colorblind or a carrier, but her mother gave her a dominant allele, and her father gave her a recessive allele.

The Inheritance Pattern for III-5

Because her grandpa on her mother's side of the family is colorblind, and he can only give the allele that he has, he passed down his recessive allele to her mother, making her mother a carrier. Her grandmother on her father's side is colorblind, and she could only pass down her recessive allele. Her father's Y chromosome could not mask this allele, causing him to be colorblind. Her father had to pass on his recessive allele, and her mother could pass on either her dominant or recessive allele, but she passed on her recessive. This inheritance is what makes III-5 colorblind.

Individual II-7: Unaffected

Genotype: XCY Phenotype: Normal Although we know this man's genotype and phenotype, we cannot assume the genotypes of his parents. His mother could have the genotype XCXC or XCXc. His father could have the genotype XCY or XcY.

Individual II-3: Carrier

Genotype: XCXc Phenotype: Normal This woman is heterozygous, but since the dominant allele has complete dominance, the dominant allele masks the recessive one. She became a carrier because her father passed down his dominant allele, and her mother gave her a recessive allele.

Individual I-3: Affected

Genotype: XcY Phenotype: Colorblind This man is red-green colorblind. Red-green colorblindness is much more common in males because this trait is recessive, but this type of colorblindness can only be masked with a dominant allele on the X chromosome. Since males do not have two X chromosomes, if they have the recessive trait, they will be red-green colorblind.

Individual II-4: Affected

Genotype: XcY Phenotype: Colorblind This man became colorblind because his mother could only pass on her recessive allele which his Y chromosome could not mask.

Individual I-2: Affected

Genotype: XcXc Phenotype: ColorblindThis woman is colorblind. Red-green colorblindness is much less common in females because it is an X-linked recessive trait, so if a female has the dominant and recessive allele, the recessive will be masked. She is homozygous recessive.

Individual I-4: Unaffected

Genotype: XCXC Phenotype: NormalThis woman is homozygous dominant so she is not affected.

Individual II-6: Carrier

Genotype: XCXc Phenotype: Normal This woman also inherited a recessive allele from her father and a dominant allele from her mother, making her a carrier.

Individual III-4: Affected

Genotype: XcY Phenotype: Colorblind This man also has a 1:1 chance of being colorblind since his mother is a carrier. He inherited his mother's recessive allele, making him red-green colorblind.

Individual III-7: Affected

Genotype: XcYPhenotype: ColorblindThis man received the recessive allele from his mother which his Y chromosome could not mask, causing him to be colorblind.