Examples of dominant and recessive traits in humans

📚 Quick Study Guide

• 🧬 Genes and Alleles: You inherit genes from your parents, and these genes come in different versions called alleles. For example, the gene for eye color has alleles for brown, blue, green, etc.
• 💪 Dominant Traits: A dominant trait is expressed when at least one dominant allele is present. We represent dominant alleles with a capital letter (e.g., 'B' for brown eyes). If you have 'BB' or 'Bb', you'll have brown eyes.
• recessive traits: A recessive trait is expressed only when two copies of the recessive allele are present. We represent recessive alleles with a lowercase letter (e.g., 'b' for blue eyes). You need 'bb' to have blue eyes.
• 👪 Genotype vs. Phenotype:
  • 🧪 Genotype: The genetic makeup (e.g., BB, Bb, bb).
  • 👁️ Phenotype: The observable trait (e.g., brown eyes, blue eyes).
• 📈 Punnett Squares: Punnett squares are used to predict the probability of offspring inheriting specific traits. They show all possible combinations of alleles from the parents.

Practice Quiz

1. Which of the following is an example of a dominant trait in humans?
   1. Attached earlobes
   2. Blue eyes
   3. Freckles
   4. Red hair
2. What genotype is required for a recessive trait to be expressed in the phenotype?
   1. One dominant allele and one recessive allele
   2. Two dominant alleles
   3. One dominant allele
   4. Two recessive alleles
3. If both parents are heterozygous (Bb) for brown eyes, what is the probability that their child will have blue eyes (bb)?
   1. 25%
   2. 50%
   3. 75%
   4. 100%
4. Which term refers to the observable characteristic resulting from the interaction of the genotype and the environment?
   1. Genotype
   2. Allele
   3. Phenotype
   4. Chromosome
5. A woman with type AB blood marries a man with type O blood. What are the possible blood types of their children?
   1. A, B, O
   2. AB, O
   3. A, B
   4. A, B, AB, O
6. What is the purpose of using a Punnett square?
   1. To determine the exact traits of the offspring
   2. To predict the probability of offspring genotypes and phenotypes
   3. To identify the dominant allele
   4. To change the genetic makeup of the offspring
7. Which of the following is an example of a recessive trait in humans?
   1. Widow's peak
   2. Dark hair
   3. Free earlobes
   4. Attached earlobes