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Understanding Mitosis, Meiosis, and Genetics

May 5, 2025

Lecture Notes: Mitosis vs. Meiosis and Genetics

Introduction

  • Lecture covers differences between mitosis and meiosis, and genetics.
  • Approach: Comparing mitosis and meiosis side by side.

Key Differences: Mitosis vs. Meiosis

  • Mitosis: Formation of somatic (body) cells.
  • Meiosis: Production of reproductive cells (gametes - sperm and egg).

Initial State

  • Both start as diploid cells (2N) with 46 chromosomes in humans (23 from each parent).
  • Interphase: Chromosome duplication occurs, but it’s not part of mitosis or meiosis.

Cell Division Sequence

  • Acronym: PMAT
    • Prophase, Metaphase, Anaphase, Telophase.
    • Meiosis stages happen twice, e.g., Prophase 1, Metaphase 1, etc.

Mitosis Phases

  1. Prophase: Chromosomes condense and become visible.
  2. Metaphase: Chromosomes align in a single row in the center.
  3. Anaphase: Chromatids separate and move to opposite ends.
  4. Telophase: New nuclear envelopes form around chromosomes.
  5. Cytokinesis: Division of the cytoplasm; results in two identical diploid cells.

Meiosis Phases

Meiosis I

  1. Prophase I: Chromosomes pair up; crossing over occurs.
  2. Metaphase I: Homologous chromosomes align in pairs.
  3. Anaphase I: Chromosomes (not chromatids) move to opposite ends.
  4. Telophase I: New nuclear envelopes form; two cells form.

Meiosis II

  1. Prophase II: Chromosomes condense (no pairing).
  2. Metaphase II: Chromosomes align in a single row.
  3. Anaphase II: Chromatids separate and move to opposite sides.
  4. Telophase II: New nuclear envelopes form; four genetically distinct haploid cells result.

Practice Questions

  • Examples of questions about phases, genetic diversity, mitosis vs. meiosis outcomes.

Genetics and Heredity

  • Heredity: Transmission of traits; involves DNA, chromosomes, and genes.
  • DNA: Encodes genetic information; influenced by environment.
  • DNA Structure: Double helix; nucleotides consist of a sugar, phosphate group, and base (A, T, C, G).

Gene Regulation

  • Not all genes code for proteins; some are regulatory.
  • Chromosomes: Structures for organizing DNA; humans have 46 (23 pairs).

Types of RNA

  • mRNA: Carries genetic code from DNA to ribosomes.
  • rRNA: Structural component of ribosomes.
  • tRNA: Transfers amino acids to ribosomes.

Protein Synthesis

  • Two main phases: Transcription (DNA to mRNA) and Translation (mRNA to protein).
    • Transcription: RNA polymerase synthesizes mRNA from DNA.
    • Translation: mRNA guides protein synthesis in ribosomes; involves tRNA.

Key Concepts

  • Codons: Groups of three bases on mRNA matched by tRNA.
  • Stop codons signal end of protein synthesis.

Practice Questions

  • Questions on transcription, roles of mRNA, tRNA, and rRNA.

Conclusion

  • Understanding differences in cell division and genetics is crucial.
  • Encouraged to practice more and utilize additional resources.

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