Lecture Notes: Genetics of Guinea Pigs

Introduction

• Confession: Desire for a hairless guinea pig in the classroom.
• Genetics of hairless guinea pigs: Fascinating due to their unique genetic makeup.

Basic Genetic Concepts

• DNA and Genes: DNA forms genes, which are inherited from both parents.
• Alleles: Different forms of a gene, represented by letters (e.g., "h" for hair).

Dominance in Alleles

• Recessive Allele: Only appears if no dominant allele is present. Represented by lowercase (e.g., "hh").
• Dominant Allele: Overrides recessive allele, represented by uppercase (e.g., "H").
• Genotypes:
  • Homozygous: Same alleles (e.g., "HH" or "hh").
    • Homozygous dominant: "HH"
    • Homozygous recessive: "hh"
  • Heterozygous: Different alleles (e.g., "Hh").

Identifying Genotypes and Phenotypes

• Hairless Guinea Pig: Must be "hh" (no dominant allele present).
• Guinea Pig with Hair: Could be "HH" or "Hh".

Monohybrid Cross

• Definition: Analyzes one trait (e.g., hair).
• Steps:
  1. Determine parent genotypes (e.g., both Hh for heterozygous).
  2. Place parent genotypes on Punnett square.
  3. Cross them to predict offspring genotypes.
• Offspring Genotypes:
  • Results: 1 HH, 2 Hh, 1 hh
  • Genotype Ratio: 1HH: 2Hh: 1hh
  • Percentage: 25% HH, 50% Hh, 25% hh

Phenotypes

• Definition: Physical traits.
• Example:
  • HH or Hh: Have hair (3 in total)
  • hh: Hairless (1 in total)
• Phenotype Ratio: 3 with hair : 1 hairless
• Percentage: 75% with hair, 25% hairless

Understanding Punnett Squares

• Purpose: Predicts probabilities of offspring traits.
• Nature of Predictions: Probabilities, not certainties (e.g., gender probability).

Conclusion

• Emphasis on Biology: Embrace the unpredictability and excitement.
• Reminder: Stay curious and engaged in learning.

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