Lecture Notes: PTC Taste Sensitivity and Genetics

Introduction

• The topic focuses on the genetic basis of being able to taste PTC (phenylthiocarbamide).
• PTC taste sensitivity is commonly used in genetic classes to illustrate inheritance and variations.

PTC Taste Sensitivity

• PTC paper has a chemical that some people find bitter, while others taste nothing.
• The ability to taste PTC is genetically determined.

Genetic Concepts

• Genes and DNA:
  • Genes: Portions of DNA that code for traits.
  • Chromosomes: 46 in humans, made up of DNA and protein.
  • Inheritance: 23 chromosomes from each parent.
• Locus and Alleles:
  • Locus: Specific area on chromosome where a gene is found.
  • Alleles: Variants of a gene, can be dominant or recessive.

PTC Taste Sensitivity as a Trait

• Genotypes and Phenotypes:
  • Genotype: Genetic makeup represented by letters (e.g., TT, Tt, tt).
  • Phenotype: Physical expression (e.g., PTC taster or non-taster).
  • Dominant allele represented by a capital letter (e.g., T), recessive by lowercase (e.g., t).
• Inheritance of PTC Taste Sensitivity:
  • TT or Tt: Genotypes that enable tasting PTC (dominant trait).
  • tt: Genotype for non-tasters (recessive trait).
• Family Example:
  • If both parents can taste PTC (Tt), their child may also have different genotypes.
  • Genotype of non-taster child would be tt.

Dominant Traits and Population Frequency

• Dominant traits are not always more common, even if they require only one dominant allele.
• Example: Polydactyly can be a dominant trait but is rare in the population.

Conclusion

• Genetic traits can be complex, involving multiple genes and interactions.
• Understanding genetic inheritance helps explain variations in traits like PTC taste sensitivity.

Additional Reminders

• Stay updated with Amoeba Sisters on Twitter and Facebook.
• Encouragement to stay curious and continue learning about genetics.