Untitled Quiz

Gregor Mendel

• Gregor Mendel was a pioneer in the field of genetics
• Lived and worked in the 19th century in Austria

Mendel's Experiments

• Mendel chose to conduct his experiments on pea plants (Pisum sativum)
• Pea plants were a good model to study inheritance because they are:
  • Easy to grow and breed
  • Have a relatively short generation time
  • Can be self-pollinated or cross-pollinated
  • Have distinct traits that are easily observable

Control of Offspring

• Mendel could be sure that all of the offspring produced were 'by his design' because he controlled pollination and fertilization

Mendel's Findings

• Phenotypic ratio in monohybrid cross: 3:1 (3 dominant: 1 recessive)
  • Example: flower color in snapdragons (P-purple, p-white)
• Phenotypic ratio in dihybrid cross: 9:3:3:1
  • Example: coat color (B-brown, b-white) and coat texture (R-smooth, r-curly) in guinea pigs

Laws of Inheritance

• Law of Independent Assortment: alleles for different genes are sorted independently during gamete formation
• Law of Segregation: each pair of alleles segregates from each other during gamete formation, resulting in each offspring receiving one allele

Punnett Squares

• Can be used to solve word problems and predict offspring genotypes and phenotypes
• 1-trait and 2-trait Punnett Squares can be used to analyze inheritance patterns

Complex Inheritance Patterns

• Incomplete dominance: one allele does not completely dominate the other allele, resulting in a blended phenotype
  • Example: flower color in petunias (R-red, r-white)
• Multiple alleles: more than two alleles exist for a particular gene
  • Example: ABO blood type (A, B, O)
• Co-dominance: both alleles are expressed equally in the phenotype
  • Example: human MN blood type (M, N)
• Pleiotrophy: one gene affects multiple phenotypic traits
  • Example: sickle cell anemia (hemoglobin, red blood cell shape)
• Polygenic inheritance: multiple genes contribute to a single phenotypic trait
  • Example: height, skin color
• Epistasis: the effect of one gene on a phenotypic trait is dependent on the presence of another gene
  • Example: flower color in corn (yellow, purple)
• Dominant but uncommon trait: a dominant allele can be rare in a population, resulting in a low frequency of the dominant phenotype

Genetic Disorders

• Recessive genetic disorders:
  • Affected individual: homozygous recessive (bb)
  • Carrier: heterozygous (Bb)
  • Unaffected individual: homozygous dominant (BB)
  • Example: cystic fibrosis
• Dominant genetic disorders:
  • No carriers, only affected and unaffected individuals
  • Example: Huntington's disease