AP Biology Questions on Sex-Linked Inheritance Patterns

🧬 Quick Study Guide

• 🔬 Sex-linked traits are those whose genes are located on the sex chromosomes (X or Y).
• 👩‍⚕️ In humans, most sex-linked traits are X-linked, as the X chromosome is much larger and carries more genes than the Y chromosome.
• 👨‍👩‍👧‍👦 Males (XY) are more likely to express recessive X-linked traits because they only have one X chromosome.
• 📈 Females (XX) must inherit two copies of the recessive allele to express the trait. They can be carriers if they have one copy.
• ✍️ Common examples of X-linked recessive traits include hemophilia and color blindness.
• ➕ X-linked dominant traits affect both males and females, but affected males pass the trait to all their daughters but none of their sons.
• 🧮 Punnett squares can be used to predict the probability of offspring inheriting sex-linked traits.

🧪 Practice Quiz

1. Which of the following statements is true regarding sex-linked traits?
   1. A) They are only expressed in females.
   2. B) They are only expressed in males.
   3. C) They are located on sex chromosomes.
   4. D) They are located on autosomes.
2. A woman who is a carrier for hemophilia, an X-linked recessive disorder, has a child with a man who does not have hemophilia. What is the probability that their son will have hemophilia?
   1. A) 0%
   2. B) 25%
   3. C) 50%
   4. D) 100%
3. Red-green color blindness is an X-linked recessive trait in humans. If a color-blind woman marries a man with normal vision, what is the expected ratio of color-blind daughters to color-blind sons?
   1. A) 1:1
   2. B) 1:0
   3. C) 0:1
   4. D) 0:0
4. A man expresses an X-linked dominant trait. Which of the following is true regarding his children?
   1. A) All of his sons will express the trait.
   2. B) All of his daughters will express the trait.
   3. C) None of his children will express the trait.
   4. D) Only some of his children will express the trait.
5. Which of the following best describes why males are more often affected by X-linked recessive traits than females?
   1. A) Males have two X chromosomes.
   2. B) Males have only one X chromosome.
   3. C) Females are always carriers.
   4. D) Females can inherit the trait from their father.
6. A female presents with an X-linked recessive disorder, indicating that:
   1. A) Her mother was a carrier and her father had the disorder.
   2. B) Her father was a carrier and her mother had the disorder.
   3. C) Both parents were unaffected.
   4. D) Only one of her grandparents had the disorder.
7. What type of inheritance pattern is characterized by the affected males passing the trait only to their daughters and never to their sons?
   1. A) Autosomal dominant
   2. B) Autosomal recessive
   3. C) X-linked recessive
   4. D) X-linked dominant