Monogenetic Inheritance

May 15, 2024

Monogenetic Inheritance

Overview

  • Focus on Specification Point B from Patterns of Inheritance
  • Today's focus: Monogenetic Inheritance
    • Mono means one; refers to the inheritance of one particular gene

Example: Pea Plants

  • Parental Phenotypes: Round and Wrinkled
  • Genotypes:
    • Homozygous dominant (Round): RR
    • Homozygous recessive (Wrinkled): rr
  • Gametes:
    • Round plant produces only R
    • Wrinkled plant produces only r
  • F1 Generation:
    • Genotype: All offspring Rr
    • Phenotype: All offspring are Round (due to dominant R)

Punnett Square

  • To show genotypic outcomes and get exam marks
  • F1 Cross: Rr x Rr
    • Possible combinations:
      • RR - Round
      • Rr - Round
      • Rr - Round
      • rr - Wrinkled

F2 Generation

  • Parental Genotypes: Both Rr
  • Gametes: Each produces R and r
  • Offspring Phenotypes:
    • 3 Round : 1 Wrinkled
    • Phenotypic Ratio: 3:1
    • Genotypic Ratio: 1 RR: 2 Rr: 1 rr
      • (1:2:1 ratio, often not asked in exams)

Important Exam Tips

  • Be descriptive: Always specify what the numbers in your ratios represent.
  • Include all elements (genotype, gametes, Punnett square) even if the final ratio is incorrect.
  • Focus more on the phenotypic ratio for exam purposes.

Summary

  • Monogenetic Inheritance: Inheritance of a single gene
  • In next sessions: Dihybrid Inheritance (two genes)
  • Keep practicing Punnett squares for accurate representation and full marks.