SexLinked

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Sex-Linked Disorders
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Sex Determination
X X

• Sex determined by genes found on the X and Y
  chromosome
• Females egg produced with an X chromosome
• Males ½ sperm cells contain X and the other ½
  contain Y
• There is a 50/50 chance of child being a boy/girl

X Y
X
X
X
X
X
X
Y
Y
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Sex-Linked Disorders

• Defined Recessive inherited conditions linked to
  the sex chromosomes
• Females XX chromosomes
• Males XY chromosomes
• More common in males because only a single X
  chromosome needs to be damaged (both must be
  damaged in females)
• Ex Colorblindness, Hemophilia, Muscular dystrophy

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Sample Colorblind Tests
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Jen is a healthy carrier of hemophilia and Adam
has no history in his family.

• What is the probability of
• getting
• Daughter with hemophilia?
• 0
• Carrier child?
• 25
• Child with hemophilia?
• 25
• Two healthy children?
• ¾ x ¾ 9/16 (56)

healthy girl
healthy girl
healthy boy
hemophilia boy
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Kelly is a healthy carrier of hemophilia, but Jim
suffers from the disease.

• What is the probability of getting a
• Healthy son?
• 25
• Healthy daughter?
• 25
• Child with hemophilia?
• 50
• Carrier child?
• 25

healthy girl
hemophilia girl
healthy boy
hemophilia boy
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Quick Review

• Sex linked disorders are found on the sex
  chromosomes
• Males more at risk due to have only one X
  chromosome
• Females carriers are normal, but can pass trait
  to future generations