D

Exam Review and Key Biological Concepts

Exam Overview

  • Exam Status:
    • Few students have yet to take the exam
  • Exam Distribution:
    • Lecture Component: 70% of the overall grade
    • Based on 3 lecture exams and up to 9 online quizzes
    • Modal Grades:
    • Most common grade: B
    • Followed closely by: A, then C
  • Office Hours:
    • Students can stop by for exam review

Gene Expression

  • Definition: The process by which information from a gene is used to produce a functional product, typically a protein.

  • Main Steps:

    1. Transcription:
    • Occurs in the nucleus
    • Produces RNA from DNA template
    • Enzyme involved: RNA polymerase
    1. Translation:
    • Occurs in the cytoplasm at ribosomes
    • mRNA is decoded to produce a polypeptide (protein)

  • DNA Template Strand: Sequence of bases (e.g., Thymine (T), Adenine (A), Cytosine (C), Guanine (G))

    • Transcription example:
    • DNA: T - A - C - G
    • mRNA: A - U - G - C

  • Codons:

    • Group of three nucleotides on mRNA
    • Examples:
    • Start codon: AUG (Methionine)
    • UCC and UCG (Serine)
    • Stop codon: UGA

Cell Division (Reproduction at the Cellular Level)

  • Parent Cell: Divides to produce two daughter cells
  • Types of Cell Division:
    • Mitotic Cell Division (M): Parent cell divides into daughter cells.
    • Cell Cycle: Sequence of stages a cell goes through, characterized by:
    1. Interphase (non-dividing phase)
    2. Mitotic Phase (dividing phase)
  • Interphase Stages:
    • G1 Phase: First gap, cell grows and duplicates organelles.
    • S Phase: Synthesis - DNA is replicated.
      • Problematic terminology: "Synthesis" should instead reference DNA replication.
    • G2 Phase: Second gap, preparation for division (protein synthesis).
  • Mitosis:
    • Involves 4 main stages:
    1. Prophase
    2. Metaphase
    3. Anaphase
    4. Telophase
    • Cytokinesis: Physical division of the cytoplasm after mitosis.

DNA Replication

  • Process:

    1. Hydrogen bonds break, DNA strands unwind.
    2. Complementary base pairing facilitated by DNA polymerase.
    3. Results in two identical DNA molecules (Semi-conservative replication)

  • Enzymes:

    • RNA polymerase (for transcription) vs. DNA polymerase (for replication)

  • Key Concepts:

    • Semi-Conservative Replication: Each new DNA molecule contains one original and one new strand.

Chromosome Concepts

  • Chromatid Structure:
    • Duplicated chromosomes consist of two sister chromatids connected at a centromere.
  • Chromosome Types:
    • Duplicated (homologous): Two sister chromatids; occurs during cell division.
    • Unduplicated: Single chromatid; occurs post-division.
  • Chromosome Count:
    • Diploid Cells: 46 chromosomes (23 pairs) in humans.
    • Haploid Cells: 23 chromosomes (gametes: sperm and eggs).

Karyotypes

  • Definition: Visual profile of the complete set of chromosomes in an individual
  • Types of Chromosomes:
    • Autosomes: First 22 pairs, carry genes for traits.
    • Sex Chromosomes: 23rd pair, determine biological sex (XX is female, XY is male)
  • Sex Determination:
    • Females inherit X from both parents, males inherit X from mother and Y from father.

Conclusion

  • Importance of understanding gene expression and cell division processes should be emphasized for exams.