Genetics Summary Notes

Cell Cycle and DNA Replication

  • Expand understanding of cell cycle and DNA replication.

Genetics Overview

  • Differentiate between somatic cells (mitosis) and gametes (meiosis).
    • Somatic cells: Diploid (2 sets of chromosomes).
    • Gametes: Haploid (1 set of chromosomes).

Mitosis vs Meiosis

  • Mitosis:
    • Goals: growth, repair, replacement.
    • Creates 2 diploid identical daughter cells.
  • Meiosis:
    • Goal: produce gametes (sperm and egg).
    • Creates 4 haploid different daughter cells.

Genes and Alleles

  • Genes: Sections of DNA encoding proteins.
  • Alleles: Different versions of a gene.
  • Homologous chromosomes: Matching chromosomes from each parent, same genes but different alleles.

Gregor Mendel

  • Austrian scientist known as the "Father of Genetics".
  • Conducted experiments using pea plants to establish inherited traits.
  • Formulated three laws of inheritance: Law of Dominance, Law of Segregation, Law of Independent Assortment.

Mendel’s Experiments

  • Controlled breeding with purebred plants only.
  • Focused on traits that had clear either-or expressions.

Crosses in Genetics

  • Cross: Mating of two organisms.
    • P = parent generation, F1 = first generation offspring, F2 = second generation offspring.

Significance of Alleles

  • Alleles represented with letters:
    • Uppercase = Dominant, e.g. A.
    • Lowercase = Recessive, e.g. a.
  • Homozygous: Same alleles (AA or aa).
  • Heterozygous: Different alleles (Aa).

Law of Dominance

  • Dominant allele expresses over recessive allele.

Genotype vs Phenotype

  • Genotype: Actual alleles inherited (e.g., FF, Ff, ff).
  • Phenotype: Physical characteristics (e.g., purple or white flowers).

Law of Segregation

  • During meiosis, each gamete receives only one chromosome from each pair.

Law of Independent Assortment

  • Alleles of multiple traits sort into gametes independently.
  • Random assortment in metaphase allows diverse combinations.

Punnett Squares

  • Diagram to predict inheritance probabilities.
  • Monohybrid cross: Examines one trait.
  • Dihybrid cross: Examines two traits (9:3:3:1 ratio for phenotypes).

Dihybrid Cross Steps

  1. Write parents' genotypes.
  2. List possible allele combinations.
  3. Fill Punnett square accordingly.
  4. Determine phenotype probabilities.