Real-world examples of dominant and recessive genes

📚 Quick Study Guide

• 🧬 Dominant Genes: These genes express their trait even when only one copy is present. Represented by uppercase letters (e.g., A).
• 🌱 Recessive Genes: These genes only express their trait when two copies are present. Represented by lowercase letters (e.g., a).
• 🧑‍🔬 Genotype: The genetic makeup of an organism (e.g., AA, Aa, aa).
• 👁️ Phenotype: The observable characteristics or traits of an organism (e.g., brown eyes, blue eyes).
• ➕ Homozygous: Having two identical alleles for a trait (e.g., AA or aa).
• ➗ Heterozygous: Having two different alleles for a trait (e.g., Aa).
• 📈 Punnett Square: A diagram used to predict the genotypes and phenotypes of offspring.

Practice Quiz

1. What is an example of a dominant trait in humans?
   1. Freckles
   2. Blue eyes
   3. Red hair
   4. Attached earlobes
2. If a person has one allele for brown eyes (B) and one allele for blue eyes (b), and brown eyes are dominant, what eye color will they have?
   1. Blue
   2. Brown
   3. A mix of brown and blue
   4. Green
3. What genotype is required for a recessive trait to be expressed in the phenotype?
   1. AA
   2. Aa
   3. aA
   4. aa
4. In pea plants, tallness (T) is dominant to shortness (t). If a heterozygous tall plant (Tt) is crossed with a homozygous short plant (tt), what percentage of the offspring will be short?
   1. 0%
   2. 25%
   3. 50%
   4. 75%
5. Which of the following is an example of a recessive genetic disorder?
   1. Huntington's disease
   2. Achondroplasia
   3. Cystic fibrosis
   4. Marfan syndrome
6. If both parents are heterozygous carriers (Aa) for a recessive disease, what is the probability that their child will have the disease (aa)?
   1. 0%
   2. 25%
   3. 50%
   4. 75%
7. In dogs, black fur (B) is dominant to brown fur (b). If a breeder crosses two dogs with the genotypes Bb, what is the probability that the offspring will have brown fur?
   1. 0%
   2. 25%
   3. 50%
   4. 75%