Cell Biology and Genetics Review

Academic Integrity and Classroom Policies

  • Recording lectures is generally not allowed unless you have an ERC (Educational Resource Center) accommodation.
  • The college discourages recording instructors without permission.
  • Phones should be put away during class.

Cell Cycle

  • S phase: DNA replication occurs.
  • S phase falls between G1 and G2 phases.

Mitosis and Meiosis

  • Organisms undergo mitosis.
  • Mitosis does not create genetic variation.
  • Following mitosis is cytokinesis.
  • Telophase: The reverse of prophase.
    • Chromosomes decondense.
    • Spindle disappears.
    • Nuclear envelope develops.
  • Meiosis:
    • Starting cell is always diploid (2n).
    • After meiosis I, two cells are produced.
    • These cells are haploid (n).
    • Nondisjunction: Chromosomes fail to separate.
      • Anaphase I nondisjunction is worse than anaphase II because all gametes will have abnormal chromosome numbers.
  • Example of sex chromosome non-disjunction: An individual having three sex chromosomes (XXY) instead of two.
  • If an organism has 2020 chromosomes in somatic cells, gametes will have 1010 chromosomes.
  • Humans:
    • Somatic cells have 4646 chromosomes.
    • Gametes have 2323 chromosomes.
    • Gametes have one sex chromosome, which becomes two upon fertilization.

Genetics

  • Codominance vs. Incomplete Dominance:
    • Codominance: Hybrids (heterozygotes) show both traits.
    • Incomplete Dominance: Hybrids show a blend of traits (e.g., white + red = pink).
  • Example of codominance in humans: ABO blood types.
  • Sex-linked traits:
    • Color blindness and hemophilia are X-linked recessive.
    • Males inherit X-linked traits from their mother.

DNA Replication and Gene Expression

  • DNA Replication:
    • Main enzyme: DNA polymerase.
    • DNA polymerase works in the 5' to 3' direction.
  • RNA Types: mRNA, rRNA, tRNA
  • Messenger RNA (mRNA) Processing:
    • Occurs before mRNA leaves the nucleus.
    • Introns are removed.
    • 5' cap is added.
    • 3' poly-A tail is added.
  • Transcription:
    • Enzyme: RNA polymerase.
    • RNA polymerase binds to the promoter.
  • Translation:
    • Location: Cytoplasm, specifically ribosomes.

Biotechnology

  • Polymerase Chain Reaction (PCR):
    • Purpose: To amplify DNA.
    • Three steps: Denaturation, Annealing, Elongation.