Amoeba Sisters Genetics Review

Overview

• Resources Provided: GIF review, study tips video, mega biology review video.
• Focus of This Review Video: Solving general genetic problems.

Key Areas Covered

1. Mendelian Genetics
   • One-Trait Crosses (Monohybrid)
   • Two-Trait Crosses (Dihybrid)
2. Non-Mendelian Traits
   • Incomplete Dominance
   • Codominance
   • Multiple Alleles
   • Sex-Linked Traits
3. Pedigrees

Important Pre-Notes

1. Materials Needed: Paper and pen/pencil.
2. Genetic Vocabulary: Assumes prior knowledge.
3. Symbols Variability: Focus on concepts, not symbols.
4. Genetic Probability: Results are probabilities, not certainties.
5. Complexity of Genetics: Beyond simple gene traits; concepts like polygenic, pleiotropic, epistasis, and epigenetics are important.

Mendelian Genetics

• One-Trait Crosses: Example of guinea pigs using a dominant "H" for hair.
  • Genotypes: HH, Hh, hh
  • Cross Example: Hairless (hh) with heterozygous (Hh)
  • Results: Genotype ratio 2 Hh: 2 hh (1:1), Phenotype ratio 2 with hair: 2 hairless (1:1).
• Two-Trait Crosses: Example using cats with fictional trait of "love for sinks" (S allele).
  • Cross Example: HhSs with HhSs
  • Gametes: HS, Hs, hS, hs
  • Phenotype Ratio: 9:3:3:1

Non-Mendelian Traits

• Incomplete Dominance: Intermediate phenotype, e.g., Snapdragons (RR, rr, Rr)
  • Ratios from Two Pink Snapdragons: Genotype 1 RR: 2 Rr: 1 rr, Phenotype 1 red: 2 pink: 1 white.
• Codominance: Both traits are fully expressed, e.g., Chickens (BB, WW, BW)
  • Cross Example: Black chicken (BB) with black and white (BW)
  • Ratios: Genotype 1 BB: 1 BW, Phenotype 1 black: 1 black and white speckled.
• Multiple Alleles: e.g., Blood types (A, B, AB, O)
  • Example Problem: Heterozygous type B and heterozygous type A parents
  • Result: 25% chance baby will be type O.
• Sex-Linked Traits: Traits on sex chromosomes, e.g., Hemophilia (Xh)
  • Example Problem: Male XhY
  • Genotypes for Hemophilia: Female XhXh, Male XhY
  • Probability Example: 0% chance of child with hemophilia from a male with hemophilia and female homozygous dominant.

Pedigrees

• Gender Representation: Circles (females) and squares (males).
• Autosomal Recessive Example: Shaded shapes = ee.
  • Analysis: Fill shaded shapes first, determine others.
  • Sex-Linked Recessive Check: Impossible offspring genotypes show it's not likely tracking sex-linked trait.

Conclusion

• Practice and Connect: Practice problems, understand real-world significance.
• Resources: Full content videos under 10 minutes available.
• Encouragement: Stay curious and continue learning about genetics.