Lecture 10, 11

• What genetic principle suggests traits blend from parents?

  Blending hypothesis
• What does the epigenesis theory propose?

  Organisms begin when parental fluids combine
• What is preformationism in genetics?

  Organisms develop from miniature, fully formed versions
• What does pangenesis theory suggest?

  Cells shed gemmules that circulate in the body
• What is the particulate hypothesis?

  Parents pass on discrete heritable units (genes)
• What does the reappearance of traits after generations indicate?

  Discrete units are inherited and can disappear
• What organism did Mendel use for his experiments?

  Garden peas
• Why did Mendel choose garden peas for his experiments?

  They are easy, cheap, and have observable traits
• What is a character in genetics?

  A heritable feature that varies among individuals
• What is a trait in genetics?

  A variant for a character, like flower color
• What is a monohybrid cross?

  Mating pairs differing in only one trait
• What happens when green and yellow pea plants are crossed?

  F1 generation produces only yellow peas

  
• What does the F2 generation reveal in Mendel's pea experiment?

  Green peas reappear, indicating recessiveness
• What is the dominant trait in Mendel's pea experiment?

  Yellow peas
• What is Mendel's proposed explanation for the 3:1 ratio?

  Two copies of each unit of inheritance
• What is a heritable factor according to Mendel?

  A gene
• What does Mendel's Law of Segregation state?

  Two alleles for a character separate during gamete formation
• What are alleles?

  Alternative versions of genes
• What happens if two alleles at a locus differ?

  The dominant allele determines appearance
• What is the significance of gamete formation in Mendel's Law of Segregation?

  Each gamete receives one gene copy randomly
• What causes wrinkled peas in Mendel's experiments?

  Non-functioning starch branching enzyme
• Why do heterozygous peas appear round?

  They have enough functional enzyme
• What is the pattern of dominance in human diseases?

  Dominant forms appear in adulthood, recessive earlier
• What does the Law of Segregation explain?

  Alleles separate during gamete formation
• How are alleles passed to progeny?

  One copy from each parent is passed on
• What is a Punnett square used for?

  To show all possible allele combinations

  
• What does a capital letter represent in genetics?

  A dominant allele
• What does a test cross determine?

  The genotype of an individual with a dominant phenotype
• What is a homozygous organism?

  Has two identical alleles for a character
• What is a heterozygous organism?

  Has two different alleles for a gene
• What is the difference between phenotype and genotype?

  Phenotype is physical appearance; genotype is genetic makeup
• What is a dihybrid cross?

  Involves two pairs of traits simultaneously
• What does the 2nd Law of Inheritance state?

  Traits assort independently during gamete formation
• What does the Principle of Independent Assortment state?

  Inheritance of one trait does not affect another
• When does the Law of Independent Assortment apply?

  To genes on different, non-homologous chromosomes
• What is complete dominance?

  Phenotypes of heterozygote and dominant homozygote are identical
• What is incomplete dominance?

  F1 hybrids show an intermediate phenotype
• What are co-dominant alleles?

  Both parental traits are expressed in offspring
• What does polymorphism refer to in genetics?

  Natural variation within a gene in a population
• What is the significance of the i allele in blood types?

  It is recessive to both IA and IB alleles