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Week 1 Case Study
Case Study: A 5-year-old boy was just diagnosed with red-green color blindness. His
parents are concerned and want clarification regarding how their son got this
disorder, as they have a daughter who does not have the disorder.
How is red-green color blindness inherited?
Red–green color blindness is passed down through an X-linked recessive
inheritance pattern. The genes that control red and green vision are located on the X
chromosome. Since males only have one X chromosome, a single mutation on that
chromosome is sufficient to cause the condition. Females, however, have two X
chromosomes, so they would need mutations on both copies to develop the disorder. If
only one chromosome carries the mutation, the second X usually prevents symptoms, and
the female becomes a carrier instead (Deeb, 2006).
In this case, the child likely inherited the affected X chromosome from his
mother. His Y chromosome, which he received from his father, does not carry the gene
for color vision. This explains why red–green color blindness is much more common in
boys than in girls (National Eye Institute, 2023).
Why doesn’t our daughter have the disorder?
Week 1 Case Study
Case Study: A 5-year-old boy was just diagnosed with red-green color blindness. His
parents are concerned and want clarification regarding how their son got this
disorder, as they have a daughter who does not have the disorder.
How is red-green color blindness inherited?
Red–green color blindness is passed down through an X-linked recessive
inheritance pattern. The genes that control red and green vision are located on the X
chromosome. Since males only have one X chromosome, a single mutation on that
chromosome is sufficient to cause the condition. Females, however, have two X
chromosomes, so they would need mutations on both copies to develop the disorder. If
only one chromosome carries the mutation, the second X usually prevents symptoms, and
the female becomes a carrier instead (Deeb, 2006).
In this case, the child likely inherited the affected X chromosome from his
mother. His Y chromosome, which he received from his father, does not carry the gene
for color vision. This explains why red–green color blindness is much more common in
boys than in girls (National Eye Institute, 2023).
Why doesn’t our daughter have the disorder?
