Mendelian genetics examples

🧬 Quick Study Guide

• 🌱 Mendel's Laws:
  • 📜 Law of Segregation: Each individual has two alleles for each trait, and these alleles separate during gamete formation.
  • 📊 Law of Independent Assortment: Alleles of different genes assort independently of one another during gamete formation. This applies when genes are on different chromosomes or are far apart on the same chromosome.
  • 👑 Law of Dominance: In a heterozygote, one allele (the dominant one) may mask the effect of another allele (the recessive one).
• 🧮 Monohybrid Cross: A cross between individuals that involves one pair of contrasting traits (e.g., $AA \times aa$). The phenotypic ratio in the F2 generation is typically 3:1 if dominance is complete.
• ➗ Dihybrid Cross: A cross between individuals that involves two pairs of contrasting traits (e.g., $AABB \times aabb$). The phenotypic ratio in the F2 generation is typically 9:3:3:1 if dominance is complete and genes assort independently.
• 🔑 Key Terms:
  • 🧬 Gene: A unit of heredity that codes for a specific trait.
  • 📍 Allele: Different versions of a gene.
  • 🏘️ Genotype: The genetic makeup of an individual (e.g., AA, Aa, aa).
  • 👁️ Phenotype: The observable characteristics of an individual (e.g., tall, short).
  • 💪 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 in a genetic cross.

🧪 Practice Quiz

1. Which of Mendel's laws states that alleles of different genes assort independently of one another during gamete formation?
   1. Law of Segregation
   2. Law of Independent Assortment
   3. Law of Dominance
   4. Law of Unit Characters
2. In a monohybrid cross, what is the typical phenotypic ratio in the F2 generation if dominance is complete?
   1. 1:1
   2. 3:1
   3. 1:2:1
   4. 9:3:3:1
3. What term describes the genetic makeup of an individual?
   1. Phenotype
   2. Genotype
   3. Allele
   4. Trait
4. An individual has two different alleles for a trait. Which term best describes this individual?
   1. Homozygous
   2. Heterozygous
   3. Dominant
   4. Recessive
5. A plant with the genotype $Aa$ is crossed with a plant with the genotype $aa$. Assuming 'A' is dominant for tall and 'a' is recessive for short, what percentage of the offspring will be short?
   1. 0%
   2. 25%
   3. 50%
   4. 75%
6. In a dihybrid cross ($AaBb \times AaBb$), assuming independent assortment, what proportion of the offspring will have the genotype $aabb$?
   1. 1/2
   2. 1/4
   3. 1/8
   4. 1/16
7. Which of the following is NOT a key concept in Mendelian genetics?
   1. Law of Superposition
   2. Law of Segregation
   3. Law of Independent Assortment
   4. Law of Dominance