Part 2

• Prokaryotes do not have a separate nucleus
• Higher organisms have a nuclear membrane around the nucleus
• Prokaryote characteristics:

  • bacteria and some algae
  • no nuclear membrane
  • no organelles
  • a circular chromosome is common
  • naked DNA
  • haploid
  • no mitotic apparatus; divide by fission
• Eukaryotes characteristics:

  • all "higher" organisms
  • have cells, each with a nucleus
  • have organelles
  • mitochondria
  • chloroplasts if plants
  • linear chromosomes
  • most often diploid; 2 sets per cell (2N)
  • DNA complexed with protein
  • mitosis and meiosis
• You get a set of chromosomes from your mom and a set from your dad
• mitosis: 2N -> two identical 2N cells

  • all chromosomes duplicate and the copies separate to daughter cells
  • each daughter cell has the same genotype
• One Aa, Bb cell always gives 2 Aa, Bb daughter cells
• meiosis: 2N -> four 1N cells in 2 divisions (M1 and M2)

  • homologous chromosomes pair in M1
  • partners of each pair go to opposite poles
  • in M2, the chromatids of each chromosome go to opposite poles
• One Aa, Bb 2N cell gives 1N gametes; They have one allele of each gene so can be AB, Ab, aB, or ab
• G1: gap 1; when the cell is growing
• S: synthesis; when the genetic information or DNA is duplicated for the next division
• G2: a gap between synthesis and mitosis; the chromosomes become condensed, visible, and separate to daughter cells
• Eukaryotes cell cycle:

  1. G1
  2. S
  3. G2
  4. mitosis
• interphase: G1, S, G2
• G1 checkpoint checks for:

  • cell size
  • nutrients
  • growth factors
  • DNA damage
• G2 checkpoint checks for:

  • cell size
  • DNA replication
• spindle assembly checkpoint checks for:

  • chromosome attachment to the spindle
• P: short arm
• Q: long arm
• signs mitosis is about to begin:

  • centriole has already duplicated
  • poles form
• meta: middle
• ana: back
• telo: end
• centrioles: microtubules in the typical 9 sets of 3 arrangement as seen in animal cells
• meiosis occurs only in germline cells
• meiosis requires two divisions following one round of DNA replication
• The critical event that differentiates meiosis from mitosis occurs in prophase of the first division M1, when the homologous chromosomes pair "gene-for-gene" throughout the length of the homologs in an event referred to as synapsis.
• The pairing and random separation of homologous chromosomes to opposite poles explains why alleles segregate.
• incomplete dominance: heterozygous phenotype is intermediate between the homozygous phenotypes
• co-dominance: when two alleles are equally dominant and equally recessive
• All probability answers must come out between 0 and 1
• Dominant genes are represented with capital letters
• Recessive genes are represented with lowercase letters
• If neither allele is dominant, it's best to use another designation and all genotypes must be defined in the legend
• P (A, B, C) (probabilities of independent events) = P(A) x P(B) x P(C)
• What is the probability that a Cc, Tt, D'D individual will produce a C, t, D gamete?

  1/8
• What fraction of the children produced by matings between Cc, Tt, D'D parents will have the same phenotype as their parents?

  P(C_) = 3/4

  P(T_) = 3/4

  P(D'D) = 2/3

  P (C_, T_, D'D) = 3/8
• If two parents have a homozygous recessive child, the trait must be recessive and each parent must be heterozygous
• What fraction of the progeny from marriages between Cc, Tt females and Cc, Tt males will be tasters or pigmented?

  15/16
• OR tells us to add