Examples of sex-linked genetic disorders in humans

📚 Quick Study Guide

• 🧬 Sex Chromosomes: Humans have two sex chromosomes: X and Y. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
• 🔗 Sex-Linked Genes: Genes located on the sex chromosomes are called sex-linked genes. Most sex-linked genes are found on the X chromosome.
• 🔴 X-Linked Recessive Disorders: These disorders are more common in males because they only have one X chromosome. If they inherit one affected X chromosome, they will express the trait. Females need to inherit two affected X chromosomes to express the trait. Examples:
  • 🩸 Hemophilia
  • 🌈 Color Blindness
  • 💪 Duchenne Muscular Dystrophy
• 🟢 X-Linked Dominant Disorders: These disorders affect both males and females, but females are often more mildly affected due to having a second X chromosome.
• ♂️ Y-Linked Disorders: These disorders only affect males because they are located on the Y chromosome.

🧪 Practice Quiz

1. Which of the following is an example of an X-linked recessive genetic disorder?
   1. Hemophilia
   2. Huntington's disease
   3. Cystic fibrosis
   4. Sickle cell anemia
2. Why are X-linked recessive disorders more commonly expressed in males than in females?
   1. Males have two X chromosomes.
   2. Males have only one X chromosome.
   3. Females have a Y chromosome.
   4. Females can never inherit X-linked traits.
3. What is the genotype of a female who is a carrier for an X-linked recessive disorder?
   1. XX
   2. XY
   3. XHXh (where XH is the normal allele and Xh is the affected allele)
   4. XhXh
4. Which genetic disorder is exclusively passed from fathers to sons?
   1. X-linked recessive
   2. X-linked dominant
   3. Y-linked
   4. Autosomal recessive
5. Color blindness is a classic example of which type of genetic disorder?
   1. Autosomal dominant
   2. Autosomal recessive
   3. X-linked recessive
   4. Y-linked
6. Duchenne Muscular Dystrophy is typically caused by a mutation on which chromosome?
   1. Y chromosome
   2. Chromosome 21
   3. X chromosome
   4. Chromosome 13
7. If a woman is a carrier for hemophilia and her partner does not have hemophilia, what is the probability that their son will have hemophilia?
   1. 0%
   2. 25%
   3. 50%
   4. 100%