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• Life cycle


  The generation-to-generation sequence of stages in the reproductive history of an organism, starting at conception until it produces its own offspring
• Somatic cell


  All cells other than sperm or ovum
• In humans, each somatic cell has 46 chromosomes, 23 homologous pairs
• We inherit one chromosome of each homologous pair from each parent
• The 46 chromosomes in a somatic cell can be viewed as two sets of 23, a maternal set and a paternal set
• Homologous chromosomes


  Chromosome pairs that carry genes that control the same inherited characters
• Fertilization and meiosis alternate in sexual life cycles
• Gametes are not produced by mitosis
• Meiosis


  The process in which the chromosome number is halved
• Human sperm or ova have a haploid set of 23 different chromosomes, one from each homologous pair
• Meiosis reduces chromosome number from diploid to haploid
• Meiosis I


  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I
• During the preceding interphase the chromosomes are replicated to form sister chromatids
• Synapsis


  Special proteins attach homologous chromosomes tightly together
• Chiasmata


  1. shaped regions where segments of the chromosomes are traded between homologous chromosomes
• Meiosis II


  1. Prophase II

  2. Metaphase II

  3. Anaphase II

  4. Telophase II
• Mitosis produces two identical daughter cells, but meiosis produces 4 very different cells
• Heritable feature


  A feature that can be passed from parents to offspring
• Character


  A heritable feature that varies among individuals
• Trait


  Variants for a character, such as purple or white color for flowers
• Mendel chose to track only those characters that occurred in two distinct alternative forms
• True-breeding


  Varieties that breed true, producing offspring identical to the parents
• Hybridization


  The process of mating two contrasting, true-breeding varieties
• P generation


  The true-breeding parents
• F1 generation


  The hybrid offspring of the P generation
• Law of Segregation


  The two alleles for a heritable character separate (segregate) during gamete formation (meiosis) and end up in different gametes
• Mendel called the purple flower color a dominant trait and the white flower color a recessive trait
• Allele


  Alternative versions of a gene
• Dominant allele


  The allele that determines the organism's appearance when the two alleles at a locus differ
• Recessive allele


  The allele that has no noticeable effect on appearance when the two alleles at a locus differ
• Homozygous


  An organism with two identical alleles for a character
• Heterozygous


  An organism that has two different alleles for a gene
• Phenotype


  An organism's physical appearance
• Genotype


  An organism's genetic makeup
• Testcross


  Breeding the mystery individual with a homozygous recessive individual to determine the genotype
• Law of independent assortment


  Each pair of alleles segregates independently of each other during gamete formation
• Dominant alleles are not necessarily more common in populations than recessive alleles
• Hardy-Weinberg Principle


  States that the frequency of dominant and recessive alleles will remain constant from generation to generation provided certain conditions exist
• If you have two alleles for a single trait, the frequency of each one must add up to 1 (p + q = 1.0, where p is the dominant allele and q is the recessive allele)
• Predictions


  • F2 generation
  • Eggs or Sperm
  • Hypothesis of dependent assortment
  • Hypothesis of independent assortment