Bio Exam 4

• Prokaryotes


  Organisms without membrane-bound organelles
• Eukaryotes


  Organisms with membrane-bound organelles
• Differences between prokaryotes and eukaryotes

  • Prokaryotes do not have organelles, eukaryotes do
  • Prokaryotes reproduce asexually through binary fission, eukaryotes reproduce sexually through mitosis/meiosis
  • Both prokaryotes and eukaryotes can undergo aerobic cellular respiration
• Histones


  Proteins that DNA wraps around for organization, too tight winding makes DNA unusable
• Histones


  Relate to gene regulation (when and where to make proteins) and to mitotic chromosomes (only formed when cells make new copies of themselves)
• Homologous pair


  Two chromosomes similar in shape and information but can have some variation (alleles)
• Mitotic chromosome


  Formed when cells make new copies of themselves
• Centromere


  Connects sister chromatids together
• Centrosome


  Connects to the microtubules
• Gene


  Genetic information to make a protein
• Allele


  Variation of a gene
• Phases of cell cycle where DNA is available for transcription and translation

  • Interphase (G1 and G2 phases)
  • Prophase
  • Telophase and Cytokinesis (Mitosis)
• During S phase of interphase, DNA replication occurs which temporarily disrupts transcription
• Growth factors


  Regulate cell cycle progression and control processes
• Checkpoints in cell cycle

  • G1: Check if DNA replication went well and DNA is not broken or mutated
  • S: Check if DNA replication is progressing and there are enough substrates
  • G2: Quality control - check DNA replication and prepare for mitosis
  • Metaphase: Check if centromeres have centrosomes so mitotic chromosomes can be pulled to equatorial plate
• If a cell fails a checkpoint, the cell cycle is halted and the cell attempts to complete DNA replication or repair damaged DNA. If damage is irreparable, the cell may undergo apoptosis.
• Ways cancer cells differ from normal cells

  • Multi-nucleated
  • Abnormal shape
  • Loss of specialization
  • No contact inhibition
  • Immortal (don't have defined lifespan)
  • Don't need growth factors
• Abnormal mitosis


  Causes cancer cells to look different (small, large, abnormal shape)
• Spending too much time in mitosis vs interphase


  Causes cancer cells to lose specialization
• End replication problem


  Chromosomes shorten at every S phase because primer on 5' end of lagging strand gets removed but cannot be fully filled in
• Telomerase


  Enzyme that increases transcription and translation, allowing cancer cells to be immortal
• Proto-oncogenes


  Normal genes that help cells progress through cell cycle
• Oncogenes


  Mutated proto-oncogenes that are more active and speed up mitosis
• Oncogene mutations are dominant, tumor suppressor gene mutations are recessive
• Tumor suppressor genes


  Genes that regulate cell division and prevent tumor formation
• Functions of p53


  • Find damaged DNA
  • Transcription factor that repairs damaged DNA
  • If not repairable, activate apoptosis
• Tumor suppressor gene mutations are recessive because both copies need to be mutated to cause changes in cell growth and tumor formation
• Apoptosis


  Regulated cell death that destroys cells from the inside out
• Steps in apoptosis


  • DNAse destroys DNA
  • Cell shape changes (blebbing)
  • Phagocytes remove cell fragments
• Functions of commonly mutated cancer genes

  • Cell growth and survival (proto-oncogenes)
  • Cell fate (stem cell signaling)
  • Genome maintenance (DNA repair enzymes)
• Diploid


  Cells containing two sets of chromosomes, one from each parent
• Haploid


  Cells containing one set of chromosomes
• Autosome


  Chromosome pair not involved in sex determination, same number in males and females
• Sex chromosome


  Chromosome involved in sex determination (males are XY, females are XX)
• Homologous chromosomes are similar in size and sequence but can have different alleles
• Cell types formed during meiosis

  • Haploid daughter cells (meiosis I)
  • Haploid gametes (meiosis II)
• Haploids must form to combine with other gametes and create genetic diversity
• Genetic diversity is good for a population to adapt to the future and avoid inbreeding
• Sources of diversity in meiosis

  • Synapsis/tetrad formation
  • Crossing over
• Independent assortment


  Alleles of different genes sort into gametes independently, travel on different homologous pairs