Mixed review

• The Amoeba Sisters have created resources for reviewing biology, including a GIF review, a study tips video, and a mega biology review video called "Stroll Through the Playlist"
• The "Stroll Through the Playlist" video was the longest video in Amoeba Sisters history
• This video will review Mendelian one-trait and two-trait crosses, as well as non-Mendelian traits like incomplete dominance, codominance, multiple alleles, and sex-linked traits, and end with pedigrees
• Things to mention before starting

  • A sheet of paper will be useful
  • Genetic vocabulary is assumed to be known
  • Genetic symbols can vary but the concept is more important
  • Genetic problems determine probability, not a guaranteed outcome
  • Genetics is complex, with topics like polygenic traits, pleiotropy, epistasis, and epigenetics
• Mendelian one-trait cross


  1. Determine genotypes of guinea pigs

  2. Cross a hairless guinea pig with a heterozygous guinea pig

  3. Determine phenotype and genotype ratios of offspring
• Mendelian two-trait cross


  1. Determine genotype of a cat heterozygous for hair and sink-loving traits

  2. Cross two cats with the same genotype

  3. Fill in a dihybrid Punnett square

  4. Determine phenotype ratio
• Incomplete dominance


  One allele is not completely dominant over the other, resulting in an intermediate phenotype
• Incomplete dominance example


  • Red snapdragon (RR) x White snapdragon (rr) = Pink snapdragon (Rr)
• Codominance


  Both traits are expressed fully
• Codominance example


  • Black chicken (BB) x Black and white speckled chicken (BW) = Black chickens and black and white speckled chickens
• Multiple alleles


  More than two alleles for a trait, as seen in blood types
• Multiple allele problem


  1. Determine genotypes for blood types A, B, AB, and O

  2. Calculate probability of a baby being type O from parents with heterozygous B and heterozygous A
• Sex-linked traits


  Traits located on sex chromosomes, usually the X chromosome
• Sex-linked trait problem


  1. Determine genotype of a male with the recessive sex-linked disorder hemophilia

  2. Identify which female genotypes would have the hemophilia disorder

  3. Calculate probability of a child having hemophilia from parents with specific genotypes
• Pedigree


  Used to track a trait of interest, with shaded shapes representing the trait
• Pedigree problem


  1. Determine genotypes of individuals in a pedigree tracking an autosomal recessive trait

  2. Explain why the pedigree is unlikely to be tracking a sex-linked recessive trait
• The Amoeba Sisters have full content videos under 10 minutes in their genetic series, and provide links to real-life examples to show the importance of understanding genetics