Non-Mendelian Genetics Summary

  • Non-Mendelian Genetics

    • Co-dominance and incomplete dominance are key concepts.
    • Multiple allelism can change dominance rules.
    • Pleiotropy occurs when one gene affects multiple traits.

  • Learning Objectives

    • Connect protein function with dominance types.
    • Understand sex-linked traits and their inheritance.
    • Apply dominance rules and probabilities to genetic crosses.

  • Important Definitions

    • Complete Dominance: One allele completely masks the effect of another.
    • Incomplete Dominance: Heterozygotes have an intermediate phenotype.
    • Co-dominance: Both alleles are expressed equally in the phenotype.
    • Multiple Allelism: More than two alleles exist for a gene in a population.

  • Blood Type Genetics

    • The gene I for blood types has three alleles: I^A (A transferase), I^B (B transferase), and i (O transferase).
    • Dominance relationship between I^A and I^B is co-dominant; both can be expressed.

  • Sex Chromosomes

    • Autosomes (1-22) are non-sex chromosomes; sex chromosomes (X, Y) determine biological sex.
    • In XY individuals, X and Y are not homologous.

  • Sex-Linked Inheritance

    • Genes outside pseudoautosomal regions (PAR) on sex chromosomes are sex-linked.
    • Example: X-linked hemophilia gene F8 is recessive.
    • Probability calculations consider the sex of both parents and offspring.

  • Pleiotropy

    • One gene can influence multiple traits, e.g., hemoglobin gene affecting blood type and malaria resistance.

  • Key True/False Statements

    • One allele can produce a full phenotype in complete dominance.
    • Multiple alleles can have different dominant relationships.
    • Pleiotropy indicates one gene controls multiple traits.
    • Sex-linked traits are not limited to recessive inheritance.
    • ABO blood type phenotype is not pleiotropic and can be classified as Mendelian.